Verb tenses and modals auxiliaries album

Verb Tenses The Present Simple Tense (also called the simple present tense) Simple present tense with 'be' The verb 'be' is different from the other verbs in this tense. Let's look at 'be' first: Here's the positive form (positive means a normal sentence, not a negative or a question. This is sometimes called 'affirmative') Positive

Positive Short Form

I am

I'm

you are

you're

he is

he's

she is

she's

it is

it's

we are

we're

they are

they're

Next, here's the negative. It's very easy. You only add 'not'.

Negative

Negative short form

I am not

I'm not

you are not

you aren't

he is not

he isn't

she is not

she isn't

it is not

it isn't

we are not

we aren't

they are not

they aren't

And finally let's talk about the question form of the present simple with 'be'.

Firstly, here's the 'yes / no' question form: Yes / No Questions am I ? are you ? is he ? is she ? is it ? are we ? are they ?

If you'd like to make a 'wh' question, you just put the question word at the front: Wh Questions where

am I ?

what

are you ?

why

is he ?

who

is she ?

when

are we ?

how

are they ?

Present simple tense with other verbs With all other verbs, we make the present simple in the same way.

The positive is really easy. It's just the verb with an extra 's' if the subject is 'he', 'she', or 'it'. Let's take the verb 'play' as an example: Positive (of 'play') I play you play he plays

she plays it plays we play they play

To make the negative form, you need to use 'do not' (don't) or ' does not' (doesn't).

Negative (of 'play') I do not play

I don't play

you do not play

you don't play

he does not play

he doesn't play

she does not play

she doesn't play

it does not play

it doesn't play

we do not play

we don't play

they do not play

they don't play

How about the question form of the present simple tense?

We use 'do' or 'does' before the subject to make the 'yes / no' question: Yes / No questions do I play ? do you play ? does he play ? does she play ? does it play ? do we play ? do they play ?

Just like with 'be', if you'd like to make a 'wh' question, you just put the question word at the front: Wh Questions where

do I play ?

what

do you play ?

why

does he play ?

who

does she play ?

when

do we play ?

how

do they play ?

Uses: 1: First, we use the Present Simple when something is generally true:   

The sun rises in the east.

People need food.

It snows in winter.

2: We also need to use this tense for a situation that we think is more or less permanent   

Where do you live?

She works in a bank.

They love coffee.

3: The next use is for habits or things that we do regularly. We often use adverbs of frequency in this case    

Do you smoke?

I play tennis every Tuesday.

We often go to the cinema.

She gets up at seven o'clock every day.

4: Four, we use the simple present to talk about what happens in books, plays, or films:   

The hero dies at the end of the film.

A young woman travels through Europe, where she meets different people, and finally falls in love.

In this book, an army invades Britain.

5: We use it in the first and the zero conditionals:  

If it rains, I won't come.

If you heat water to 100 degrees, it boils.

6: Strangely, we can use this tense to talk about the future. When you are discussing a timetable or a fixed plan, you can use this tense.   

School begins at nine tomorrow.

Our train leaves at eleven.

What time does the film start?

7: We also use it to talk about the future after words like ' 'when', 'until', 'after', 'before' and 'as soon as' in a future sentence:   

I will call you when I have time. (Not: 'will have') I won't go out until it stops raining.

She'll come as soon as her babysitter arrives.

8: We need to use this simple tense with stative verbs (verbs which we don't use in continuous tenses), in situations where we'd usually use the present continuous:   

This soup tastes great.

You look fabulous.

I think she is very pretty.

How to make the Present Continuous Tense (also called the Present Progressive Tense) The present continuous (sometimes called the present progressive) tense in English is really easy to make and is the same for all verbs. We make it using the present simple of 'be' + verb-ing: Here is how we make the positive: Positive

Positive Short Form

I am sleeping

I'm sleeping

you are sleeping

you're sleeping

he is sleeping

he's sleeping

she is sleeping

she's sleeping

it is sleeping

it's sleeping

we are sleeping

we're sleeping

they are sleeping

they're sleeping

We can make the negative by adding 'not': Negative

Negative Short Form

I am not sleeping

I'm not sleeping

you are not playing

you aren't playing

he is not reading

he isn't reading

she is not working

she isn't working

it is not raining

it isn't raining

we are not cooking

we aren't cooking

they are not listening they aren't listening

Questions are also really, really easy. Just like we made the question with 'be' in the present simple, here we also put 'am', 'is', or 'are' before the subject to make a 'yes / no' question: Yes / No Questions am I eating chocolate ? are you studying now ? is he working ? is she doing her homework ? is it raining ? are we meeting at six ? are they coming ?

For 'wh' questions, just put the question word at the front: Wh Questions Why am I eating chocolate ?

What are you studying now ?

When is he working ?

What is she doing ?

Why is it raining ?

Who are we meeting ?

How are they travelling ?

Uses: 1: First, we use it for things that are happening at the moment of speaking.   

I'm working at the moment.

Please call back as– we are eating dinner now.

Julie is sleeping.

2: We can also use this tense for temporary situations, when we feel something won't continue for a long time.   

She's staying with her friend for a week.

I'm living in London for a few months.

John's working in a bar until he finds a job in his field.

3: We can use the present continuous for habits but they have to be temporary or new habits   

He's eating a lot these days.

She's swimming every morning (she didn't use to do this).

You're smoking too much.

4: Another present continuous use is for annoying habits, when we want to show that something happens too often and we don't like it. In this case we usually use an adverb like 'always', 'forever' or 'constantly'.   

You're always losing your keys!

She's constantly missing the train.

He's always sleeping in.

5: The next use is for definite future arrangements (with a future time word). In this case we have already made a plan and we are pretty sure that the event will happen in the future.   

I'm meeting my father tomorrow.

We're going to the beach at the weekend.

I'm leaving at three.

6: Finally we use this tense to talk about a situation which is slowly changing.

 

I'm getting better at playing the piano.

The weather is improving.

The Present Perfect Simple Tense To make the positive present perfect tense, use:   

'have' / 'has' + the past participle Make the past participle by adding 'ed' to regular verbs (for example, 'play' becomes 'played') There are a few verbs that change their spelling when you add 'ed' (for example, 'study' becomes 'studied')

Positive

Positive Short Form

I have played

I've played

you have worked

you've worked

he has written

he's written

she has walked

she's walked

it has rained

it's rained

we have travelled

we've travelled

they have studied

they've studied

The negative is really simple too. Just put 'not' after 'have' or 'has': Negative

Negative Short Form

I have not eaten breakfast today

I haven't eaten

you have not been to Asia

you haven't been

he has not seen the new film

he hasn't seen

she has not played tennis

she hasn't played

it has not snowed this winter

it hasn't snowed

we have not slept all night

we haven't slept

they have not tried the food

they haven't tried

To make a question, put 'have' or 'has' in front of the subject: Yes / No' Questions have I missed the bus? have you visited London? has he worked as a waiter before? has she met John? has it been cold this week? have we arrived too early? have they studied English grammar before?

As you can imagine, for 'wh' questions, we just put the question word before 'have' or 'has': 'Wh' Questions where have I left my umbrella? what have you done today? why has he gone already? where has she been in the UK? why has it rained so much this summer? what have we done? where have they learned English before?

Uses: 1: Life experience (we don't say when the experience happened, just sometime in the past)   

I have been to Tokyo.

She has lived in Germany.

They have visited Paris three times.

2: A finished action with a result in the present (focus on result)

  

I've lost my keys (so I can't get into my house).

She's hurt her leg (so she can't play tennis today).

They've missed the bus (so they will be late).

3: With an unfinished time word (this month, this week, today, in the last year)   

I haven't seen her this month.

She's drunk three cups of coffee today.

This week they've been shopping four times.

The present perfect continuous tense (also called the present perfect progressive) Here's the positive (it's the present perfect of 'be' + verb -ing): Positive

Positive Short Form

I have been walking

I've been walking

you have been running

you've been running

he has been cooking

he's been cooking

she has been swimming

she's been swimming

it has been raining

it's been raining

we have been studying

we've been studying

they have been sleeping

they've been sleeping

To make the negative, just add 'not': Negative

Negative Short Form

I have not been walking

I haven't been walking

you have not been running

you haven't been running

he has not been cooking

he hasn't been cooking

She has not been swimming

she hasn't been swimming

it has not been raining

it hasn't been raining

we have not been studying

we haven't been studying

they have not been sleeping

they haven't been sleeping

Can you guess how to make the question form of the present perfect continuous? It's not very difficult - just put 'have' or 'has' before the subject: 'Yes / No' Questions have I been walking? have you been running? has he been cooking? has she been swimming? has it been raining? have we been studying? have they been sleeping?

For 'wh' questions put the question word first: 'Yes / No' Questions what have I been doing? where have you been running? what has he been studying? why has she been working today? how long has it been raining? how long have we been watching this film? how long have they been living here?

Uses: 1: To say how long for unfinished actions which started in the past and continue to the present. We often use this with for and since.   

I've been living in London for two years.

She's been working here since 2004.

We've been waiting for the bus for hours.

2: Actions which have just stopped (though the whole action can be unfinished) and have a result, which we can often see, hear, or feel, in the present (focus on action).   

I'm so tired, I've been studying.

I've been running, so I'm really hot.

It's been raining, the pavement is wet.

The Past Simple Tense (also called the simple past tense) It's similar to the present simple because it has different rules for the verb 'be', which becomes 'was' or 'were': The Past Simple with 'be' Here's how to make the positive: Positive with 'be' I was cold you were tired he was in the garden she was late it was sunny we were on holiday they were hungry

To make the negative with 'be', just add 'not': Negative Negative Short with Form 'be' I was not sleepy

I wasn't sleepy

you were not on the bus

you weren't on the bus

he was not at school

he wasn't at school

she was not beautiful

she wasn't beautiful

it was not cold

it wasn't cold

we were not at work

we weren't at work

they were not tired

they weren't tired

To make a question, just like the present simple, we change the position of 'was / were' and the subject.

Here are the past simple 'yes / no' questions with 'be': 'Yes / No' Questions with 'Be' was I sleepy? were you late? was he at the cinema? was she kind? was it hot? were we hungry? were they at work?

And the 'wh' questions with 'be' (the question word just goes at the beginning, everything else is the same): 'Wh' Questions with 'Be' why was I sleepy? where were you? when was he at the cinema? how was she? how was it? why were we hungry?

when were they at work?

The Past Simple (Simple Past) with Other Verbs Positive with Other Verbs I walked (regular) you played (regular) he cooked (regular) she listened (regular) it rained (regular) we ate (irregular) they drank (irregular)

In the negative there aren't any irregular verbs. All verbs use 'did not (didn't) + infinitive': Negative

Negative Short Form

I did not walk

I didn't walk

you did not play

you didn't play

he did not cook

he didn't cook

she did not listen

she didn't listen

it did not rain

it didn't rain

we did not eat

we didn't eat

they did not drink

they didn't drink

Questions are also very easy. Just put 'did' before the subject, and the infinitive after it.

Here are the 'yes / no' questions: 'Yes / No' Questions did I walk?

did you play? did he cook? did she listen? did it rain? did we eat? did they drink?

To make a 'wh' question, of course, put the question word at the beginning of the sentence: 'Wh' Questions where did I go? what did you play? what did he cook? why did she listen? when did it rain? where did we eat? how did they travel?

Here's when we use it: 1: Finished events in the past with no connection to the present:  

Leonardo painted the Mona Lisa.

The Vikings invaded Britain.

2: With a finished time word (yesterday, last week, at 2 o'clock, in 2003):  

I went to the cinema yesterday.

We visited Japan in 2007.

3: For stories / lists of events:

 

He went to a café, sat down and lit a cigarette.

Yesterday I went to the library, met a friend for lunch, and played tennis.

4: Details of news:  

I've hurt my leg. I fell off a ladder when I was painting my bedroom.

I've been on holiday. I went to Spain and Portugal.

5: As part of the second conditional:  

If I won the lottery, I would buy a house in Chelsea.

If she knew his number, she would call him.

The Past Continuous (or past progressive tense) How can we make the past continuous? Firstly, check that you know how to make the past simple with 'be' (subject + was / were). Then just add verb-ing.

Here's the positive form:       

I was sleeping you were working he was coming she was reading 'War and Peace' it was raining we were shopping they were watching a film

Next, here's the negative - it's very easy, just add 'not':       

I was not (wasn't) sleeping you were not (weren't) working he was not (wasn't) coming she was not (wasn't) reading 'War and Peace' it was not (wasn't) raining we were not (weren't) shopping they were not (weren't) watching a film

And, just like the past simple with 'be', to make a 'yes / no' question, put 'was / were' in front of the subject:  

Was I listening?

Were you working?

    

Was she working?

Was he living in Paris at the time?

Was it snowing when you arrived?

Were we eating?

Were they studying?

To make a 'wh' question (of course) put the question word at the beginning:       

Why was I working?

Where were you living?

How was she travelling?

Where was he going?

Why was it snowing in the summer?

What were we eating?

Why were they studying?

Uses: 1: A continuous action in the past which is interrupted by another action or a time:  

I was taking a bath when the telephone rang.

At three o'clock, I was working.

2: Background information, to give atmosphere to a story: 

It was a beautiful day. The birds were singing, the sun was shining and in the cafes people were laughing and chatting.

3: An annoying and repeated action in the past, usually with 'always': 

He was always leaving the tap running.

4: For two actions which happened at the same time in the past: 

I was watching TV and he was reading.

The Past Perfect Tense The positive - make it with 'had' + the past participle (usually made by adding 'ed' to the infinitive, but a few verbs have irregular past participles):      

I had been (I'd been) You had gone (you'd gone) She had met (she'd met) He had played (he'd played) It had rained (it'd rained) We had bought (we'd bought)



They had studied (they'd studied)

The short form for 'had' is 'd.

(Be careful not to confuse it with 'would'. Would is followed by the infinitive - 'I'd go', whereas had is followed by the past participle - 'I'd gone').

For the negative just add 'not':       

I had not been (I hadn't been) You had not gone (you hadn't gone) She had not met (she hadn't met) He had not played (he hadn't played) It had not rained (it hadn't rained) We had not bought (we hadn't bought) They had not studied (they hadn't studied)

And to make a 'yes / no' question put 'had' before the subject:       

Had I come?

Had you eaten?

Had she gone?

Had it rained?

Had he studied?

Had we met?

Had they left?

For 'wh' questions put the question word at the beginning:       

When had I come?

Why had you eaten?

Where had she gone?

When had it rained?

Why had he studied?

How had we met?

When had they left?

Uses: 1: A completed action before something else in the past. 

When we arrived, the film had started.

2: To explain or give a reason for something in the past. 

I'd eaten dinner so I wasn't hungry.



It had snowed in the night, so the bus didn't arrive.

3: Stative verbs only: something that started in the past and continued up to another action in the past. 

When he graduated, he had been in London for six years.

4: As part of the third conditional. 

If I had known you were ill, I would have visited you.

The Past Perfect Continuous Here's how to make the past perfect continuous. It's 'had' + been (the past participle of 'be')+ verb-ing Firstly, let's look at the positive form:    

I had been living You had been going She had been sleeping He had been working

Next, the negative form:       

I had not been trying (I hadn't been..)

You had not been working (you hadn't been..)

She had not been crying (she hadn't been..)

He had not been shopping (he hadn't been..)

It had not been snowing (it hadn't been..)

We had not been reading (we hadn't been..)

They had not been running (they hadn't been..)

It's pretty easy to make the question too.

'Yes / no' questions:       

Had I been working?

Had you been sleeping?

Had she been reading?

Had he been watching TV? Had it been raining?

Had we been drinking?

Had they been eating?

'Wh' questions:

      

Where had I been working?

How long had you been sleeping?

What had she been reading?

How long had he been watching TV? How long had it been raining?

What had we been drinking?

Why had they been eating?

Uses: 1: Something that started in the past and continued up to another action or event (tells us 'how long') 

She had been working at that company for a year when she met James.

2: Cause of something in the past 

The pavement was wet, it had been raining.

The Simple Future Tense (or future with will) Here's the positive form (it's just 'will' + infinitive):       

I will meet him later (I'll ..)

You will come (you'll..)

It will rain tomorrow (it'll) She will be late (she'll..)

He will help us later (he'll..)

We will get married in September (we'll) They will cook dinner (they'll..)

Next, here's the negative form (just add 'not' - remember will not = won't):       

I will not go (I won't ..)

You will not be late (you won't ..)

It will not snow tomorrow (it won't..)

She will not get the job (she won't..)

He will not pass the exam (he won't ..)

We will not come (we won't..)

They will not stop (they won't ..)

Finally, here's the question: 'yes / no' questions:       

Will I go?

Will you come early?

Will it be cold?

Will she dance?

Will he arrive soon?

Will we cook?

Will they leave?

'wh' questions:       

Where will I go?

Why will you come early?

When will it be cold?

Who will she dance with?

What time will he arrive?

What will we cook?

When will they leave?

Uses: 1: A decision at the moment of speaking:  

A: 'I'm cold'.

B: 'I'll close the window'.

2: Prediction based on opinion: 

I think the Conservatives will win the next election.

3: A future fact: 

The sun will rise at 7am.

4: Promises / requests / refusal / willingness:   

I'll help you with your homework.

Will you give me a hand?

I will give up smoking!

5: In the same way as the future continuous, but with state verbs: 

I'll be at the station when you arrive.

We use 'be going to' + infinitive for: 1: Future plans made before the moment of speaking:  

A: 'We've run out of milk.'

B: 'I know, I'm going to buy some.'

2: Prediction based on present evidence: 

Look at those boys playing football! They're going to break the window.

The Future Continuous (or future progressive tense) Here's how to make it: The positive (will + be + verb-ing):       

I will be sleeping you will be working she will be studying it will be raining he will be cooking we will be eating breakfast they will be travelling

Here's the negative: When John gets home,       

I will not be working (I won't be ..) you will not be reading (you won't be ..) he will not be cooking (he won't be ..) she will not be studying (she won't be ..) it will not be snowing (it won't be ..) we will not be watching TV (we won't be ..) they will not be sleeping (they won't be ..)

Next, the question: 'yes / no' questions:   

will I be cooking? will you be dancing? will she be singing?

   

will he be eating? will we be drinking? will it be snowing? will they be talking?

'wh' questions:       

what will I be doing? where will you be working? how will she be travelling? what will he be eating? why will we be studying? why will it be snowing? what will they be wearing?

Uses: 1: A continuous action in the future which is interrupted by a time or by another action.  

I’'ll be waiting when you arrive.

At eight o’clock, I’'ll be eating dinner.

2: A complete action in the future that will happen in the normal course of events.  

The Government will be making a statement later.

Will you be taking your car to the meeting?

3: To make a guess about the present. 

My mother will be working now

The future perfect is made with the future simple of 'have' (will have) and the past participle. For regular past participles add 'ed' to the verb ('play' becomes 'played').

Here's the positive: By six pm tonight:     

I will have finished this book You will have studied the English tenses She will have cooked dinner He will have arrived We will have met Julie

 

It will have stopped raining They will have left Japan

Here's the negative:       

I will not have finished this book You will not have studied the English tenses She will not have cooked dinner He will not have arrived We will not have met Julie It will not have stopped raining They will not have left Japan

To make the question, just put 'will' before the subject: 'Yes / no' questions:       

will I have finished writing this book? will you have studied all the English verb tenses? will she have graduated? will he have got married? will it have got colder? will we have met your boyfriend? will they have left their jobs?

'Wh' questions:       

When will I have finished writing this book?

Why will you have studied all the English verb tenses by tomorrow?

When will she have been here three weeks?

Why will he have got married before June?

Why will it have got colder by May? How will we have met your boyfriend by tonight?

When will they have left their jobs?

Uses: 1: With a future time word, (and often with 'by') to talk about an action that will finish before a certain time in the future, but we don't know exactly when.  

By 10 o'clock I will have finished my homework.

By the time I'm sixty, I will have retired.

The Future Perfect Continuous Tense (also called the future perfect progressive) Positive Form

Positive Short Form

I will have been working

I'll have been working

You will have been sleeping

You'll have been sleeping

She will have been studying

She'll have been studying

He will have been cooking

He'll have been cooking

It will have been raining

It'll have been raining

We will have been exercising

We'll have been exercising

They will have been travelling

They'll have been travelling

Negative Form

Negative Short Form

I will not have been working

I won't have been working

You will not have been sleeping

You won't have been sleeping

She will not have

She won't have

been studying

been studying

He will not have been cooking

He won't have been cooking

It will not have been raining

It won't have been raining

We will not have been exercising

We won't have been exercising

They will not have been travelling

They won't have been travelling

'Yes / No' Questions       

Will I have been working?

Will you have been sleeping?

Will she have been studying?

Will he have been cooking?

Will it have been raining?

Will we have been exercising?

Will they have been travelling?

'Wh' Questions      

Where will I have been working?

Why will you have been sleeping?

Where will she have been studying?

What will he have been cooking?

How long will it have been raining?

Where will we have been exercising?

Uses: 1: With a time word, to talk about an action which starts before a time in the future and continues up to that time. 

In April 2009, I will have been teaching here for two years.

Modal Auxiliaries: The modal auxiliaries (or modals) include the following: can, could, may, might, must, should, will, would Modals are always followed by the base form of a verb or auxiliary verb.

Modals are always the same form no matter what the subject is.

In standard American English, a predicate verb phrase cannot contain more than one modal. correct He will be able to go. not correct He will can go.

Below are example sentences containing the modal may and the verb go. Notice that the form of the modal does not change.        

I may go.

You may go.

He may go.

It may go.

We may go.

They may go.

He may have gone.

They may have gone.

Modals and related verb phrases add meanings to verbs. Below are some of those meanings: Ability/Availability future: will be able to present: can, am/is/are able to past: could, was/were able to Requests present/future: can, could, will, would Permission future: will be allowed to present/future: may, can, could, am/is/are allowed to past: could, was/were allowed to Possibility present/future: may, might, could past: may have, might have, could have

Impossibility present/future: couldn’t, can’t past: couldn’t have Advisability present/future: should, ought to, had better past: should have, ought to have, had better have Expectation present/future: should, ought to past: should have, ought to have Necessity future: will have to present/future: must, have to, has to past: had to Lack of Necessity future: won’t have to present/future: don’t have to, doesn’t have to past: didn’t have to Prohibition present/future: must not, may not, cannot past: could not Logical Deduction (=Probability) present: must, have to, has to past: must have, have to have, has to have SOCIAL MODALS The choice of modal depends partly on the social situation.

We often use formal language with strangers (people we don’t know) and superiors (people with some power over us such as our employers, doctors, and teachers).

We often use informal language with our equals (our friends and family) and subordinates (people we have some power over such as our employees or children).

General requests (present and/or future):    

Will you help me? (Informal Are you willing?)

Would you help me (Formal Are you willing?)

Can you help me? (Informal Are you able?)

Could you help me (Formal Are you able?)

Requests for permission (present and/or future):    

May I leave the room? (Formal) Might I leave the room? (Formal rarely used) Could I leave the room? (Less formal Can I leave the room? (Informal)

Expressing suggestions, advice, warnings, necessity (present and/or future): The choice of modal depends partly on the urgency of the message or the authority of the speaker/writer or both.

Suggestions:  

You could see the doctor.

You might see the doctor.

Advice:  

You should see the doctor.

You ought to see the doctor.

Warning/strong advice: 

You had better see the doctor.

Strong advice/necessity:   

You have to see the doctor.

You have got to see the doctor.

You must see the doctor.

No choice: 

You will see the doctor.

MODALS OF BELIEF (beliefs about present time) The choice of modal depends partly on what the speaker or writer believes.

-Someone is knocking at the door:  

That could be Fred.

That might be Fred.

= It’s possible. I’m less than 50% sure. 

That may be Fred.

= It’s possible. I’m less than 60% sure.  

That should be Fred.

That ought to be Fred.

= I’m expecting Fred and I think he’s here.   

That must be Fred.

That has to be Fred.

That has got to be Fred.

= It’s probably Fred. I have a good reason to believe it is Fred. 

That will be Fred.

= I believe it is Fred. I’m about 99% sure.  

That can’t be Mary.

That couldn’t be Mary.

= It’s impossible. I’m about 99% sure. 

That is Fred.

= I know it’s Fred. I’m 100% sure.

MODALS OF BELIEF (beliefs about past time) The choice of modal depends partly on what the speaker or writer believes.

-Someone was knocking at the door:  

That could have been Fred.

That might have been Fred.

= It’s possible. I’m less than 50% sure. 

That may have been Fred.

= It’s possible. I’m less than 60% sure.  

That must have been Fred.

That has to have been Fred.



That has got to have been Fred.

= It was probably Fred. I have a good reason to believe it was Fred. 

That couldn’t have been Mary.

= It’s impossible. I’m about 99% sure. 

That was Fred.

= I know it was Fred. I’m 100% sure.

MODALS OF BELIEF (beliefs about future time) The choice of modal depends partly on what the speaker or writer believes.

-What will the weather be like tomorrow?  

It could rain tomorrow.

It might rain tomorrow.

= It’s possible. I’m less than 50% sure. 

It may rain tomorrow.

= It’s possible. I’m less than 60% sure.  

It should rain tomorrow.

It ought to rain tomorrow.

= I expect it will rain. 

It will rain tomorrow.

= I believe it is going to rain. I’m about 99% sure. 

It couldn’t snow tomorrow.

= It’s impossible. I’m about 99% sure.