A complementary good or service is something used or provided in combination with another good or service. The word complementary means combining to enhance or emphasize each other's qualities.

Yalcin, Taylan, Elie Ofek, Oded Koenigsberg, and Eyal Biyalogorsky. "Complementary Goods: Creating, Capturing, and Competing for Value." Marketing Science 32, no. 4 ...

dismiss an opposition to the registration of WATERFORD STELLENBOSCH for wine. The board held that since the goods covered by the proposed registration were complementary to glassware products covered ...

In Nanu-Nana v OHIM, the General Court has upheld a decision of the First Board of Appeal of OHIM allowing an opposition to the registration of the mark NANU for certain goods and services based on a ...