The indefinite article has two forms: before singular nouns one uses "a" (or "an" before most vowels); before plural nouns one uses "some":
But: before vowels producing a "y" sound (as in "you"), "a" is used, rather than "an":
As a general rule, the indefinite article signals a person, thing or event that has not been clearly defined by the speaker. It does not indicate a specific objection (which is the role of the definite article); rather, it indicates any one object out of many possible ones (in the singular), or any assortment or quantity from many possible assortments or quantities (in the plural). It is often used after verbs of possession or consumption:
In the negative, the plural indefinite article changes: "some" is generally replaced by "any" (this change also occurs in negative questions) :
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