a/an—Indefinite Article

• Used when we (speaker and listener) don’t know which one, or it doesn’t matter which one
• I need a cup; could you get me one, please? (It doesn’t matter which one, I just need a cup.)
• She wants a doll for her birthday.

• Used to talk about any one member of a class.
• A car is a necessity for many people. (any car)
• An elephant is big and gray.

• Used to classify people or things.
• She’s a waitress.
• “What’s that?” “Oh, it’s just a wind chime, that’s all.”

• Plural and uncountable nouns generally do not get an article—use some or any.
• I saw some geese flying overhead.
• Water, milk, bread, sugar, etc.
• Please give me some juice.
• Do you have (any) money?
• The store was out of butter.

• When “a/an” is necessary:
• Negative expressions
• “Let me borrow your calculator.” “I don’t have a calculator.” (Not I don’t have calculator.)

• Prepositions
• He sat down in the shade of a tree. (Not … of tree.)

• Fractions
• two-thirds of a mile (Not two-thirds of mile)

• When “a/an” is NOT used:
• With adjectives alone (without a noun).
• It’s a nice day. (The article is used, since there is a noun.)
• It’s nice. (Not It’s a nice.)

• Possessives—use the phrase a _______ of mine/yours/ etc.
• She’s my teacher.
• She’s a teacher of mine.