Illustrated using a corpus of three hundred sentences, the present study aims to study, following the functionalist model initiated by André Martinet, the different types of complement function in isángu. It emerges from this study that isángu attests to three types of complement function: the object complement function, the complement function of determination and the circumstantial complement function. They can be assumed by several monemes, in particular, nominals, phrases, adverbs, numerals, infinitive, demonstratives and totalizer. Keywords: add-in function, add-in, isangu, syntax