This is a grammar of Suki, a Trans New Guinea language spoken by approximately 7500 people living in and around a lagoon, close to the Fly River, in the Western Province of Papua New Guinea. The data for this grammar was collected during 18 months of fieldwork. Suki has a rich verb morphology. It inflects for up to three arguments and one of 15 tense–aspect–mood–polarity values. Verbs often occur in serialisation. Verbless and copular clauses are also frequently used. Central to the grammar of Suki is the tamp-particle unit, a paradigm of forms of which one representative is required in every main clause. The tamp-particle unit is, on the one hand, an information structuring device, and on the other, a marker of tense–aspect–mood– polarity, which interacts with the marking on the verb. Through its omnipresence, it has a structuring role in many of the language’s constructions, including clause combining and insubordination.