Northern Mao is an endangered Afroasiatic-Omotic language of western Ethiopia with fewer than 5,000 speakers. This study is a comprehensive grammar of the language, written from a functional/typological perspective which embraces historical change as an explanation for synchronic structure. The grammar introduces the Northern Mao people, aspects of their culture and history, and the major aspects of the language: contrastive phonology, tone phenomena, nouns, pronouns, demonstratives, numerals, noun phrases, verbs and verbal morphology, single verb constructions, non-final/medial clauses, subordinate clauses and alignment. The tone system has three contrastive levels, where the Mid tones subdivide into two classes which historically derive from two different sources. Nouns each exhibit two tonal melodies: one melody in citation form or other unmodified environments and another melody when syntactically modified. Extensive coverage is given to developments in the pronominal and subject-marking systems as well as the verbal system. In the pronominal and subject marking systems, innovations include the development of a dual opposition, the fusion of an affirmative verbal prefix to subject prefixes, and the development of these subject prefixes into new pronouns. In the verbal system, innovations include the development of new verbal wordforms from subordinate + final verb periphrastic constructions and a set of new subject markers from an old subordinator morpheme. The verbal system is oriented around two oppositional relations: realis vs. irrealis and finite vs. infinitive verb forms. Realis and irrealis verbs have distinct item-arrangement patterns: realis verbs take subject prefixes while irrealis verbs take subject suffixes. Realis is associated with affirmative polarity and non-future tense and may be used with many aspectual distinctions. Irrealis is associated with negative polarity, future tense, and counterfactual constructions; irrealis verbs do not express many aspectual distinctions. Finite versus infinitive verb stems are differentiated by tone. Finite verb stems are used in affirmative declarative and interrogative utterances, non-final/medial constructions and the more finite subordinate clause structures. Infinitive verb stems are used in negative declarative and interrogative utterances, non-final/medial constructions and the less finite subordinate clause structures. The work concludes with a summary of cross-constructional alignment patterns and evaluates the efficacy of a marked-nominative analysis. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]