This book is based on a typological/functional perspective which provides an excellent framework for writing a broadly useful, descriptive grammar. Retuarã, is also know as Letuama (Tanimuca-Retuarã, Retuama, Letuhama, Ufaina, Uairã) is a member of the central Tucanoan language family and is closely related to Tanimuca. Though the Retuarã and Tanimuca peoples consider themselves as separate groups, they speak the same language with slight lexical differences. Their location is in widely distributed areas of the Amazon Basin in southeastern Colombia has brought them into contact with other Tucanoan and Arawakan languages resulting in some grammatical variations. Besides a brief phonological sketch and description of various aspects of the Retuarã language, the study presents a detailed discussion of parts of the speech, the noun phrases, case, the verb phrase, adverbs, sentence structure, imperatives, questions, negation, subordination, and various elements of discourse.