Originally Posted by Bogota63
completes, while a compliment
"She complimented him on the way the nose ring complemented his outfit."
Source The UVic Writer's Guide: Complement / Compliment
Originally these two spellings were used interchangeably, but they have come to be distinguished from each other in modern times. Most of the time the word people intend is “compliment": nice things said about someone ("She paid me the compliment of admiring the way I shined my shoes.”). “Complement,” much less common, has a number of meanings associated with matching or completing. Complements supplement each other, each adding something the others lack, so we can say that "Alice’s love for entertaining and Mike’s love for washing dishes complement each other.” [Complement
means “something that completes or brings to perfection”.] Remember, if you’re not making nice to someone, the word is “complement.”
Test your understanding of the homophones compliment and complement by choosing the correct word in each of the following sentences.
1. When he joined as a much-needed bass player, John acted as a (complement/compliment) to the band.
2. Jane’s boss is always giving her (complements/compliments) about the way that she answers the phone.
3. That scarf really (complements/compliments) Susan’s complexion.
4. Coach Miles (complemented/complimented) his team on a terrific win.
5. In order to meet customer demands, Sunny Corporation must use a full (complement/compliment) of 50 employees.
Answers can be found here Grammatically Correct: Complement versus Complimentt