Without assuming arbitrary restrictions on grammar notation at the outset, 'Bare Grammars' aim to provide the most straightforward definitions of the constructions present in human languages, together with a compositional semantics. A simple generative approach is presented which induces a natural algebraic notion of structure, with the surprising result that not only classical syntactic relations (like c-command) but also certain morphological relations concerning identity of particular morphemes (e.g. case markers) are properly structural. Formal models of case marking, verb voice, anaphora, are considered, and linguistic universals are proposed that do not assume any kind of structural isomorphism between languages. A strong form of compositionality is defended, together with the hypothesis that grammatical morphemes ('syntactic constants') always denote semantic constants, revealing that the relation between form and meaning is not subject to arbitrary dictates of linguistic convention, history, and accidents of human biology.