SUMMARY.Responses to the Terman-Merrill Vocabulary Test, Form L-M, of 100 children at each of five age-levels from 6 to 14 years in a judgment sample of 65 Northern Ireland schools were scored for 10 categories of definition. Factor analysis confirmed that two categories, Synonym and Explanation, might be combined as Abstract responses. Ordered stepwise regression confirmed the significance, as hypothesised, of age, occupation and joint age-by-occupation effects, in that order, for Abstract and Total responses. The joint effect was greater for Abstract responses, and showed that children of non-manual fathers differ progressively with age from children of manual fathers for those forms of definition, such as synonyms and explanations, that showed the strongest pattern of development with age.