伊(yī) - he, she, that one (literary third person) in Mandarin

伊 (yī) is a third-person pronoun, but not the one you will use at the bus stop. It belongs to classical Chinese, to poetry, and to a handful of southern dialects, where it covers he and she alike. In modern standard writing it survives mostly as a deliberate literary touch.

You will also meet 伊 constantly as a sound rather than a word, because it transcribes foreign names and places: 伊拉克 (Iraq), 伊朗 (Iran), 伊丽莎白 (Elizabeth). In those the character carries no meaning at all.

The trap for English speakers is treating 伊 as a live alternative to 他 and 她. It is not. Say 伊 in conversation and you sound like a subtitle from a period drama. Recognise it when you read it, and leave it there.