What words mean, Lewis Carroll’s Humpty Dumpty suggests, depends only on individuals’ asserting their authority to give them a particular meaning, but Alice and others question this claimed semantic authority. Dictionaries are often thought of as semantically authoritative, but most aim to describe actual usage, not to endorse ‘proper’ meanings. For words like tree names, semantic authority plausibly lies with those who know about trees. But even in sciences, semantic authority is disputable, as shown by debates over defining planet. Sometimes courts adjudicate conflicts over meanings, as illustrated by shifts in marriage and related words. Even then divergent interests can allow continuing disputes. Guidelines for ‘inclusive language’ sought to direct people to use words in certain ways. Their effective authority was tied to the issuing group’s status: government agencies, e.g, could better wield semantic authority than small interest groups. Policing others’ usage sometimes happens and is called ‘political correctness’ (PC); mocking others’ usage often accompanies charges of being PC. Claims of trans women that they themselves know best whether they are women are sometimes derided. But such first-person semantic authority gains its force from existence of communities recognizing the legitimacy of such gender claims. Ultimately, semantic authority resides in communities.