余 / 吾【yú / wú】

余 and 吾 both mean "I" in classical Chinese. Neither is used in speech. You meet them in quotations, in prefaces and old letters, and in modern essays where the writer wants an old-fashioned or mock-solemn voice.

吾 as "my"

吾 can stand straight before a noun and mean "my" or "our", with no 的.

吾辈 and 吾等

吾辈 – "people like us", "our generation" – is still alive in written rallying calls and in prefaces. 吾等 is "we" in the voice of a historical novel.

余 or the other 余

余 more often means "remaining" or "more than": 其余 "the rest", 三十余人 "more than thirty people". The "I" reading has a verb right after it, usually at the start of a clause.

In modern prose

A modern writer who uses 吾 is being playful or grand on purpose. Swapped into an ordinary sentence, it sounds like a joke.

• × 吾今天去超市买东西 → 我今天去超市买东西

汝 is the matching classical "you", and turns up in the same kinds of text.