Complementarily is an adverb that denotes two things working together to complete a whole. Synonyms for complementarily include synergistically, reciprocally, cooperatively, harmoniously, congruently, coordinately, in concert, together, simultaneously, in tandem, and correspondingly. These words suggest two or more things working hand-in-hand to enhance the overall effect. Other synonyms for complementarily include complementally, supplementally, augmentatively, reinforcingly, and supportively. These words are used to describe two or more things that combine to create a more comprehensive result. No matter which word you choose, it's clear that complementarily has a rich variety of synonyms to choose from.