May \May\, v. [imp. Might] [AS. pres. m[ae]g I am able, pret. meahte, mihte; akin to D. mogen, G. m["o]gen, OHG. mugan, magan, Icel. mega, Goth. magan, Russ. moche. ?. Cf. Dismay, Main strength, Might. The old imp. mought is obsolete, except as a provincial word.]

An auxiliary verb qualifyng the meaning of another verb, by expressing:
   (a) Ability, competency, or possibility; -- now oftener expressed by can.

How may a man, said he, with idle speech, Be won to spoil the castle of his health ! --Spenser.

For what he [the king] may do is of two kinds; what he may do as just, and what he may do as possible. --Bacon.

For of all sad words of tongue or pen The saddest are these: ``It might have been.'' --Whittier.
   (b) Liberty; permission; allowance.

Thou mayst be no longer steward. --Luke xvi. 2.
   (c) Contingency or liability; possibility or probability.

Though what he learns he speaks, and may advance Some general maxims, or be right by chance. --Pope.
   (d) Modesty, courtesy, or concession, or a desire to soften a question or remark.

How old may Phillis be, you ask. --Prior.
   (e) Desire or wish, as in prayer, imprecation, benediction, and the like. ``May you live happily.'' --Dryden.

May be, & It may be, are used as equivalent to possibly, perhaps, by chance, peradventure. See 1st Maybe.

Source: Webster's Revised Unabridged Dictionary (1913)