A philosophical theory of language can aim for completeness in either of two senses. It may strive for "horizontal completeness", which would require it to give an account of all parts of languagesingular terms, predicates, verbs, adverbs, adjectives, nondeclarative sentences, speech acts, etc. Alternatively, it may strive for "vertical completeness", analysing some linguistic notions in terms of others, but ultimately providing an analysis of language which does not take any semantical or linguistic notions as primitive.