IPA: /ˌkɒmplɪˈmɛntərɪli/
KK: /ˌkɒmplɪˈmɛntərɪli/
In a way that adds to or completes something else, often enhancing its quality or effectiveness.
The two colors work complementarily to create a beautiful design.
Complementarily → It is formed from "com-" (meaning together) and "plement" (from Latin "complementum", meaning that which completes) and the suffix "-arily" (meaning in a manner). The word "complementarily" refers to the manner in which two or more things complete or enhance each other together.
Think of things that work 'together' ('com-') to 'complete' ('plement') each other — that's what complementarily means.