Students ages 12, 15, 18, and 23 (n = 60 per group) wrote definitions for 16 abstract nouns (e.g., pride, courage, realization). Responses were analyzed for the Aristotelian style, a type of definition that mentions both the superordinate category term and one or more characteristics of the word (e.g., "Pride is a sense of delight about a possession or accomplishment"). This response type was of interest because it is a sophisticated and literate defining style that is modeled in classrooms, textbooks, and dictionaries-a style that is informative, concise, and efficient. The results indicated that a number of important changes occur in the ability to provide Aristotelian definitions for abstract nouns during the developmental period from late childhood to early adulthood. Specifically, there was an increasing tendency for students to mention the appropriate category to which a word belongs, core features of the word, and subtle aspects of meaning. The study contributes to the knowledge base concerning the nature of language development in pre-adolescents, adolescents, and young adults.