Please note: I am still working on this page...
can / could
The speaker says that something is possible or impossible because of the law, physical or mental ability, logic or science, custom or morality... or a combination of these.
For a table of examples with remote forms, click here .
To see tables of the frequency of words used with "could" , click here.
may / might
... for possibility.More subjective than "can/could"
It may/might (not) rain
It may/might (not) be raining
It may/might (not) have rained
It may/might (not) have been raining
... for permission. The speaker gives permission, ...or refuses it
You may (not) sit here.
(might is not used here, it is too remote)
shall / should
With "will" , the speaker says that something is inevitable,
with "shall" there is more of the speaker's personal involvement.
You shall be there at 6:30 ( I order you )
We shall not warn you again (... that is a promise)
Shall we go out?
For "should" Lewis (LTP) gives 5 distinct groups:
" If he should be late..."/"Should he be late..." = If he is late...
"Should you not contact us..." = If you do not contact us...
"You should watch that video" = I think you will enjoy it
"You should have taken a taxi" = ...but you did not take a taxi
"You should not watch so much TV" = I recommend you do not watch so much
"You should not have eaten that fish" = It was a bad idea
"We suggest that passengers should carry only 5kg" = It is best if...
"I should think he's in Paris" = In my estimation he is there
"You shouldn't have any problems" = I don't think you will...
How should I know? = Don't ask me!
will / would
The graphic below shows how the modal verb goes together with other auxiliary and main verbs, and it also shows the approximate frequency of these combinations with " would".
" would " is the most frequent modal verb ( BNC )
" will " is also very common, but it has another written form ( -'ll) and a great range of attitude and meaning depending on intonation and stress in speech.
GRAMMAR + VOCABULARY + CONTEXT = MEANING
"Context" includes the relationship between the speaker or listener, writer or reader.
For example, there is a form called "future perfect" or "future anterior" which is usually presented to learners as a " completed action in the future", predicted by the speaker.
a medical expert, interviewed by a journalist about a recently successful operation to separate conjoined twins said " It will have been a very difficult procedure".
a press officer, talking about the latest photographs of a train accident : " You will have seen the photos of the damage ..."
a teacher, writing on a web page :" Most students of English will have learned that "will" is "the future form in English"
...these forms are frequent, a search of the BNC with the term " will + have + vbn " will give examples of the form with past, current and future references. They use "will " to emphasise that they are giving an opinion about current and past fact.
Most common uses are for
an offer:- " I'll help you " / "I'll make some coffee"
a promise or a threat. You decide which, depending on the situation:- " I'll see you tomorrow" / " I will always love you" / " You will never see me again" / " It will be a cold day in hell before I help you again!"
negotiation:- " I'll pay you an extra 3% if you can deliver on Friday" / " For an extra 5% I'll deliver it tomorrow"
prediction- science/ astrology/ fortune telling:- " There will be rain tomorrow in the west and north" / "Capricorns will have a good year"
a speaker's view of habit/liklihood:- "He'll be at home in bed now" / " She'll be working all next week"
"-'ll"- relaxed future marker ( what is any view of the future, if not an opinion?) Mixed in with any other prospective language forms e.g. be + -ing , be going to , first form verbs which may be independent of any modal. Find your own examples.
restaurant/ shopping:- "I'll have fish" / " I'll take it"
authority/announcement :- " The Court will rise" / " You will not use your computer for playing games" / " The Queen will not visit Margate this year"
It's wrong to ignore the social and personal implications of these uses. And there can be a crossover between the above areas. Check with a search on the BNC or with the COBUILD corpus. As noted above, a search for any of the modal perfect forms (a modal + have) will throw up some interesting results, and that's a promise.
" would" is the remote form of " will"...