A pronoun was the grammatical term for a word that substituted for a noun, such as "he" or "she." In many languages, pronouns varied depending on the gender of the antecedent.
When Malcolm Reed and Charles Tucker spent two days on Risa in 2152, they looked for female companionship. Tucker commented about an alien that he found her interesting, to which Reed replied "I don't think "she" is the right pronoun." (ENT: "Two Days and Two Nights")
The androgynous J'naii used a neutral pronoun; Soren did not believe there was a good translation for this pronoun into English. While working with the J'naii in 2368, William T. Riker had trouble constructing sentences without gender-based personal pronouns. (TNG: "The Outcast")
After Ezri Dax had been joined with the Dax symbiont in 2375, she sometimes confused pronouns when mixing memories from the various former hosts of the symbiont; early on she stated "these pronouns are going to drive me crazy." (DS9: "Afterimage", "Prodigal Daughter")
When Adira Tal first came aboard the USS Discovery, the crew assumed they were female and referred to them using "she/her" pronouns. Adira later confided in Paul Stamets that they were actually non-binary and asked to be referred to using gender-neutral "they/them" pronouns. Stamets and the rest of the crew promptly began doing so. (DIS: "The Sanctuary")
According to a deleted scene from "Broken Bow", the Rigelian language had a pronominal base, i.e. the language was based on pronouns.