Adjectives are a powerful tool for enriching vocabulary and developing conceptual understanding. In primary classrooms, across core and foundation subjects, children are expected to describe, measure, classify, and compare objects and events - all processes that require a mastery of adjective meanings and use. While teachers are trained in vocabulary learning, they are less likely to be familiar with the psychological processes by which children learn adjectives. To address this gap, we provide an accessible primer of relevant research findings on adjective development, with guidance on how they can be used to enhance current teaching and learning practices across subjects at Key Stage 1. As an author team with linguistic, psychological, and pedagogical expertise, we synthesise research from across these disciplines to provide an evidence-based, practical guide for practitioners supporting 5-7 year-old children.