a

Andy Samberg Hi-Fives A Bobcat ...
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before countable or singular nouns referring to people or things that have not already been mentioned: ◆a man / horse / unit ◆ an aunt / egg / hour / x-ray ◆ I can only carry two at a time. ◆ There's a visitor for you. ◆ She's a friend of my father's (= one of my father's friends).
Brooks : The parole board got me into this halfway house called "The Brewer" and a job bagging groceries at the Foodway.
Brooks : Maybe I should get me a gun,

before uncountable nouns when these have an adjective in front of them, or phrase following them: ◆a good knowledge of French ◆ a sadness that won't go away
Ellis Boyd 'Red' Redding : I remember my first night. Seems like a long time ago.
Ellis Boyd 'Red' Redding : a free man at the start of a long journey whose conclusion is uncertain.

any; every:◆ A lion is a dangerous animal.

a member of a group or profession: ◆Their new car's a BMW. ◆ She's a Buddhist. ◆ He's a teacher. ◆ Is that a Monet (= a painting by Monet)?
Andy Dufresne : I had to come to prison to be a crook.
Ellis Boyd 'Red' Redding :the part of you that knows it was a sin to lock them up does rejoice,

in front of two nouns that are seen as a single unit: ◆a knife and fork

instead of one before some numbers: ◆A thousand people were there.

when talking about prices, quantities and rates
Synonym: PER
◆They cost 50p a kilo. ◆ I can type 50 words a minute. ◆ He was driving at 50 miles an hour.

a person like sb: ◆She's a little Hitler.

before sb's name to show that the speaker does not know the person: ◆There's a Mrs Green to see you.

before the names of days of the week to talk about one particular day: ◆She died on a Tuesday.

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