may, might and could - what's the difference

OK, I'm confused now, or at least I might be.

Totally agreed!!! I have just finished checking my "Grammar for English Language Teachers" (published by the Cambridge University Press) and I still cannot really find / find out the answer, particularly between "might" and "may" when expressing possibility.

Well, I guess I will just (have to) (hey, another model verb!) tell my students that it is more about the tone and intonation when speaking.

Again, I am so grateful to find your views / suggestions here!  I feel so relieved and I think I can go to bed now!

 

Miss Frances - ESL Instructor, Hong Kong Baptist University, Hong Kong

 

 

Mary Ansell's on-line text, English Grammar: Explanations and Exercises, explains some of the differences among these auxiliaries:

3. Can and Could

The modal auxiliary can is most often used in the Simple conjugation.

The most important meaning of can and could is to be able to.
e.g. He can walk thirty miles a day.
      When she was young, she could swim across the lake.
The first example has the meaning, He is able to walk thirty miles a day. The second example has the meaning, When she was young, she was able to swim across the lake.

Like the auxiliary would, could can be used in polite requests and suggestions.
e.g. Could you please tell me how to get to Almond Street?
      You could try asking the bus driver to help you.

As indicated in the previous chapter, could can be used in sentences expressing wishes.
e.g. He wished he could visit France.
      I wish I could have helped you.

See Exercise 6.

It has also been pointed out that could can be used in either the main clause or the subordinate clause of a statement expressing a false or improbable condition.
e.g. If he were stronger, he could help us push the car out of the snow.
      She could have caught the bus if she had left right away.
      I would be glad if I could help you.
      If he could have solved the problem, he would have felt happier.

See Exercises 7 and 8.

In informal English, can is often used with the meaning to be allowed to.
e.g. He says I can take the day off.
      Can I have some more soup?

However, in formal English, it is considered more correct to use the auxiliary may in such situations.
He says I may take the day off.
May I have some more soup?

 
4. May, Might and Must

One of the meanings of may and might is to be allowed to.
e.g. The members of the organization agree that I may join it.
      The members of the organization agreed that I might join it.

The auxiliary must is a stronger form of may and might. One of the meanings of must is to be obliged to or to have to.
e.g. You must provide proper identification in order to cash a check.
      They must work harder if they are to succeed.

It should be noted that the meaning of must not is to be obliged not to.
e.g. You must not leave.
      He must not speak.
The first example has the meaning, You must stay. The second example has the meaning, He must be silent.

In order to express the idea of not being obliged to do something, an expression such as not to be obliged to or not to have to is generally used.
e.g. You do not have to leave.
      He is not obliged to speak.
The first example has the meaning, You may stay, if you wish. The second example has the meaning, He may be silent, if he wishes.

Like could and would, might can be used in polite requests and suggestions. The auxiliaries could, would and might can be used to express differing degrees of politeness:

Degree of Politeness    Auxiliary
  somewhat polite      could
  quite polite      would
  very polite      might

Thus, might expresses the highest degree of politeness.
e.g. Might I observe what you are doing?
      Might I offer some advice?

See Exercise 9.

May, might and must are also used to express differing degrees of probability:

Degree of Probability    Auxiliary
  somewhat probable      may, might
  highly probable      must

For instance, may and might are often used in the Simple conjugation to express the idea that an event is somewhat probable.
e.g. You might be right.
      It may snow later this afternoon.

Similarly, must can be used in the Simple conjugation to express the idea that an event is highly probable.
e.g. He must be mistaken.

In the following examples, the Perfect conjugations with may, might and must are used to express differing degrees of probability relating to past events.
      Rupert might have taken the money, but it seems unlikely.
      It is possible he may have called while we were out.
      It must have rained last night, because the streets are wet.


The entire book is available at:   http://www.fortunecity.com/bally/durrus/153/gramtoc.html

Webster's 1828





MAY, n. [L. Maius.]

1. The fifth month of the year, beginning with January, but the third, beginning with March, as was the ancient practice of the Romans.
2. A young woman.
3. The early part of life.
His May of youth and bloom of lustihood.
MAY, v.i. To gather flowers in May-morning.

MAY, verb aux; pret.might.

1. To be possible. We say, a thing may be, or may not be; an event may happen; a thing may be done, if means are not wanting.
2. To have physical power; to be able.
Make the most of life you may.
3. To have moral power; to have liberty, leave, license or permission; to be permitted; to be allowed. A man may do what the laws permit. He may do what is not against decency, propriety or good manners. We may not violate the laws, or the rules of good breeding. I told the servant he might be absent.
Thou mayest be no longer steward. Luke 16.
4. It is used in prayer and petitions to express desire. O may we never experience the evils we dread. So also in expressions of good will. May you live happily, and be a blessing to your country. It was formerly used for can, and its radical sense is the same.
May be, it may be, are expressions equivalent to perhaps, by chance, peradventure, that is, it is possible to be.







MIGHT, n. pret. of may. Had power or liberty. He might go, or might have gone.

1. It sometimes denotes was possible, implying ignorance of the fact in the speaker. Orders might have been given for the purpose.
MIGHT, n.

1. Strength; force; power; primarily and chiefly, bodily strength or physical power; as, to work or strive with all one's might.
There small be no might in thy hand. Deut.28.
2. Political power or great achievements.
The acts of David--with all his reign and his might.
1 Chron.29. l Kings 15.

3. National strength; physical power or military force.
We have no might against this great company that cometh against us. 2 Chron.20.
4. Valor with bodily strength; military prowess; as men of might. 1 Chron.12.
5. Ability; strength or application of means.
I have prepared with all my might for the house of my God--1 Chron.29.
6. Strength or force of purpose.
Like him was no king that turned to the Lord with all his might. 2 Kings 23.
7. Strength of affection.
Thou shalt love the Lord thy God with all thine heart, and with all thy soul,and with all thy might. Deut.6.
8. Strength of light; splendor; effulgence.
Let them that love him be as the sun when he goeth forth in his might. Judges 5.
Shakespeare applied the word to an oath. "An oath of mickle might." This application is obsolete. We now use strength or force; as the strength or force of an oath or covenant.

With might and main, with the utmost strength or bodily exertion; a tautological phrase, as both words are from the same root, and mean the same thing.







COULD, pron. COOD. [The past tense of can, according to our customary arrangement in grammar; but in reality a distinct word, can having no past tense. Could, we receive through the Celtic dialects.]

1. Had sufficient strength or physical power. A sick man could not lift his hand. Isaac was old and could not see. Alexander could easily conquer the effeminate Asiatics.
2. Had adequate means or instruments. The men could defray their own expenses. The country was exhausted and could not support the war.
3. Had adequate moral power. We heard the story, but could not believe it. Th intemperate man could have restrained his appetite for strong drink. He could have refrained, if we would.
My mind could not be towards this people. Jeremiah 15.
4. Had power or capacity b the laws of its nature. The tree could not grow for want of water.
5. Had competent legal power; had right, or had the requisite qualifications. Formerly, a citizen could not vote for officers of government without the possession of some property. AB could not be elected to the office of senator, for want of estate. BC, not being the blood of the ancestor, could not inherit his estate.
6. Had sufficient capacity. The world could not contain the books. John 21.
7. Was capable or susceptible, by its nature or constitution, as of some change. He found a substance that could not be fused.
8. Had adequate strength or fortitude; as, he could not endure the pain or the reproach.
9. Had motives sufficient to overcome objections. He thought at first he could not comply with the request; but after consideration he determined to comply.
10. Had competent knowledge or skill. He could solve the most difficult problems.