They Definition

thā

he, it, she

pronoun

The persons, animals, or things previously mentioned.

Webster's New World

Used to refer to the one previously mentioned or implied, especially as a substitute for generic he .

Every person has rights under the law, but they don't always know them.

American Heritage

People.

They say it's so.

Webster's New World

The person or group just mentioned.

Everyone thinks they are right about this issue.

Webster's New World

Used to refer to people in general.

American Heritage

Synonyms:

determiner

(archaic or dialectal) Those (used for people)

Wiktionary

Origin of They

Cognate to Old English þā (“those") (whence Modern English tho), Scots thae, thai, thay (“they; those"), Icelandic þeir (“they"), Faroese teir (“they"), Swedish de (“they"), Danish de (“they"), Norwegian de (“they"), Norwegian Nynorsk dei (“they"), and German die (“the; those", plural article and pronoun). See also tho.

From Wiktionary
The term was borrowed by Middle English (as they, thei) in the 1200s from Old Norse þeir, the nominative plural masculine of the demonstrative sá, which acted in Old Norse as a plural pronoun. The Norse term derives from Proto-Germanic *þai (“those"), from Proto-Indo-European *to- (“that"). It gradually replaced Old English hÄ« and hÄ«e (“they").

From Wiktionary
Middle English from Old Norse their masculine pl. demonstrative and personal pron. to- in Indo-European roots

From American Heritage Dictionary of the English Language, 5th Edition
The term has been used as a singular pronoun since at least the 1400s.

From Wiktionary