To reciprocate means to respond to something by doing the same thing back. When your friend helps you with homework and you later help them study for a test, you're reciprocating their kindness. When someone waves at you and you wave back, you're reciprocating their greeting.

The word suggests a natural back-and-forth exchange. If you invite someone to your birthday party, you might hope they'll reciprocate by inviting you to theirs. When countries reciprocate trade agreements, each offers the other similar benefits. Good friendships work because both people reciprocate: one person listens, the other listens back; one shares, the other shares in return.

Reciprocation doesn't always mean doing exactly the same thing. If your neighbor brings you cookies when you're sick, you might reciprocate by mowing their lawn while they're away. The key is responding to a gesture with a gesture of similar value or kindness.

When someone doesn't reciprocate, the relationship feels one-sided and eventually breaks down. If you always help a classmate but they never help you back, they're not reciprocating. The best relationships, whether friendships or partnerships, thrive on mutual reciprocation, where both sides naturally give and receive.