quid pro quo

An equal exchange or substitution, as in I think it should be quid pro quo—you mow the lawn and I'll take you to the movies. This Latin expression, meaning “something for something,” has been used in English since the late 1500s.

A fair exchange; the phrase is most frequently used in diplomacy: “The Chinese may make some concessions on trade, but they will no doubt demand a quid pro quo, so we must be prepared to make concessions too.” From Latin, meaning “something for something.”