Source : Webster's Revised Unabridged Dictionary (1913)

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 mought is obsolete,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}.