In many languages the form of one word depends on the form of another. Agreement is the grammatical requirement that certain words share features such as person, number, gender, or case.

Subject-verb agreement is familiar in English: she walks versus they walk. Richer systems mark adjectives and determiners to match nouns, or require verbs to agree with both subject and object. When agreement fails, sentences sound unfinished or non-native.

Agreement helps listeners track who did what in complex clauses. Acquisition researchers study when children master these dependencies. Typologists classify languages by how extensively they require agreement and which features participate.

• Matching of grammatical features across words
• Commonly involves person, number, and gender
• Links subjects and verbs, nouns and modifiers
• Varies widely in richness across languages