Abstract“Trait” is a ubiquitous term in biology, but its precise meaning and theoretical foundations remain opaque. After distinguishing between “trait” and “character,” I argue for the value of adopting Theodosius Dobzhansky’s 1956 definition and framework for understanding “trait,” which holds that traits are just “semantic devices” that artificially impose order on continuous biological phenomena. I elaborate on this definition to distinguish between trait validity (compliance with Dobzhansky’s trait definition) and trait utility (usefulness of a trait). As a consequence of this (...) elaboration of the meaning of “trait,” it becomes clear that considerations of adaptation, function, homogeneity and natural kinds have clouded discussions of the meaning of “trait” per se. Combining this account with work by David Hull and examples from contemporary biology, I demonstrate that even broad or heterogeneous traits (including multiple sub-traits) can qualify as valid and useful. As a test case for this understanding of trait, I show how it can help resolve critiques of schizophrenia’s status as a single trait, highlighting the recent advances made within schizophrenia research. (shrink)