Agreement in language relates to the correspondence between words in a sentence, in terms of gender, case, person, or number. For example, in the sentence he runs, the suffix -s agrees with the singular he. Patterns of agreement vary dramatically cross-linguistically, with great diversity in the way it is expressed, and the types of variation permitted. This textbook offers an insight into how agreement works, and how linguists have tried to account for it. It will be essential reading for all those studying the structure and mechanisms of natural languages.