So I understand that I�d better disregard what�s written in the grammar book, and also what was taught by two Americans, who are also English graduated teachers. In fact I don�t know Bruce but for me is difficult to disregard what was taught by people who have a master degree in English (and are Americans as well).

I agree that people use language in different ways in different regions, but it can�t be used as standard. There are some Portuguese rules that are not used in Brazil, but as a Portuguese teacher I have to teach them.

Zailda you are like a lot of my Asian staff. "If it is print it is correct"  We discussed this in my Ethics for Teachers class and we found the typical textbook on this subject is up to the whim of the printer.  Not all in print is correct and not all Native English teachers are correct but have to agree with those that you disagree with on this one.  "May, might and could" are probably something will happen while the word "must" is more of a demand or guarantee it will happen.  This is not an American English thing it is a standard English rule.  I found that mistake in my text here on what it sounds like you were talking about; it was a poor copy of a British textbook based out of Hong Kong press using the original text book cover.  I am sitting with the original British textbook and the one used at my school going over the rules in it for my lesson.  The changes are obvious between the two and they have the same cover.  Sadly the company that I am using this poor copy is a very well known ESL academy with schools around the world.

G�day strangers!

Just to add my 2 cents worth�

Zailda � it�s certainly reasonable that you may have been taught the �degrees of probability/possibility� by American trained native English speakers. It could also be that they might have been regurgitating what they were taught without actually thinking about the way in which the language is actually applied!

But I would also have to say that according to Swann�s �Practical English Usage�  (in his 3^rd edition, anyway) Zailda has it right!

As others here have observed, English textbooks (& texts in general) may have many errors & could conflict with observations & nuances detailed by many native (or near native) English speakers� I won�t go into what I consider to be the reasons for this in this comment, however!

In my experience:

�May � � tends to be used as a more polite form of �might� in my experience of common usage.

Might is usually more casual & perhaps even rhetorically used as a preference to �may�.

�Could � is often used to introduce a speculative consideration that invites further discussion of the reason or likelihood of an occurrence.

But, as with all English, there are many possibilities because of variation in English dialects.

To sum up, I agree with Bruce & Roneydirt about the interchangeability & contemporary use of may/might/could but also support Zailda�s comments about probability/certainty, particularly as Swann has said as much - & I�m sure he�s done far more research on this than I have!

Cheers & Happy St Nicholas� Day to you all.

Good morning, everyone,�

I would like to thank all the people who tried to help me explain the grammar point. I am more than satisfied with the answers I got and I think that after balancing the different points of view I am able to make my own conclusion.�

You all were very helpful to me, good job�

Wish a a beautiful day, mine is just �starting

Mish

Bruce and AB have summed it up pretty well--we native speakers don �t usually learn how to use our English words from a language book.