Functionalist accounts of language suggest that forms are paired with meanings in ways that support efficient communication. Previous work on grammatical marking suggests that word forms have lengths that enable efficient production, and previous work on the semantic typology of the lexicon suggests that word meanings represent efficient partitions of semantic space. Here we consider an integrated information-theoretic framework that captures how communicative pressures influence both form and meaning. We take tense systems as a case study, and show how the framework explains both which tense systems are attested across languages and the length asymmetries of the forms in those systems.