they,they/them Singular “they” TRUE they them their theirs themselves TRUE TRUE Singular “they” has been used in English to describe an unspecified person since the late 1300s (it's even older than singular “you”!). Nowadays, it's the most popular choice among people who prefer gender neutral forms. It starts being {https://www.merriam-webster.com/words-at-play/singular-nonbinary-they=accepted by dictionaries} too.
it,it/it,it/its Personal “it” TRUE it it its its itself FALSE FALSE Although “it” is normally used for objects, not people, some actually do like being called that way. If someone wants you to call it “it”, it's not offensive – it's actually respectful.
one,one/one,one/one's Specific “one” TRUE one one one's one's oneself FALSE FALSE “One” is used in formal English when talking about a general or a hypothetical person. Recently people started using “one” also as their personal pronoun.