what is the definition of using 'a' in a sentence?

what is the definition of using 'a' in a sentence?

example:

my sister is a lawyer.

why do we use 'a'?

hope i make sense!!:-D

Quote:

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Originally Posted by arabica

what is the definition of using 'a' in a sentence?
example:
my sister is a lawyer.
why do we use 'a'?
hope i make sense!!:-D

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"a" is an indefinite article
for further information see:
http://owl.english.purdue.edu/handouts/esl/eslart.html

thanks !... i went on the site and its helped alot!!