Verbs and nouns are fundamental units of language, but their neural instantiation remains poorly understood. Neuro- psychological research has shown that nouns and verbs can be damaged independently of each other, and neuroimaging re- search has found that several brain regions respond differen- tially to the two word classes. However, the semantic–lexical properties of verbs and nouns that drive these effects remain unknown. Here we show that the most likely candidate is pre- dication: a core lexical feature involved in binding constituent arguments (boy, candies) into a unified syntactic–semantic structure expressing a proposition (the boy likes the candies). We used functional neuroimaging to test whether the intrinsic “predication-building” function of verbs is what drives the verb–noun distinction in the brain. We first identified verb- preferring regions with a localizer experiment including verbs and nouns. Then, we examined whether these regions are sensitive to transitivity—an index measuring its tendency to select for a direct object. Transitivity is a verb-specific prop- erty lying at the core of its predication function. Neural activ- ity in the left posterior middle temporal and inferior frontal gyri correlates with transitivity, indicating sensitivity to predi- cation. This represents the first evidence that grammatical class preference in the brain is driven by a wordʼs function to build predication structures.