Maybe - may be

These two terms are etymologically connected. Grammatically, they are very different. (Here is a case where the space between words matters.) They are pronounced virtually identically, however, a speaker who wants to be clear will sometimes have a micropause between may and be when using the two-word version.

• Maybe (one word) is an adverb. (Etymologically, it is a shortened form of a verb phrase, "it may be".) It means roughly the same as "perhaps". As a rule of thumb, use the one-word maybe with two commas, one before it and one after. It may help you to think that the one-word "maybe" is the one used in speech when we don't want to make a definite answer: "Did you go in my purse?" says the mother; and the sulky child may say "Maybe" - as this is a well-educated sulky child, the answer is written as a single word adverb.

• The two words may be, as a unit, belong in a verb phrase. They may be - as they are here - modal auxiliary + verb ('to be'); or they may be being used - as in this second example - as modal auxiliary + auxiliary be-progressive + -ing participle of the verb (copula 'to be'). Use no commas with the two words may be, and use the two separate words where they express the main idea in the sentence.

For a similar error, see Every day - everyday.