re: They're, Their, There Now.

quote:

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Ain't

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Merriam Webster
1 : am not : are not : is not
2 : have not : has not
3 : do not : does not : did not — used in some varieties of Black English
Origin: contraction of are not.
First use: 1749


Usage: Although widely disapproved as nonstandard and more common in the habitual speech of the less educated, ain't in senses 1 and 2 is flourishing in American English. It is used in both speech and writing to catch attention and to gain emphasis. Our evidence shows British use to be much the same as American.