1. the state or condition of being in harmony or agreement. Affective concordance is said to exist, for instance, when facial gestures mirror internal states of feeling, such as frowning when perplexed or annoyed, or when two or more individuals related through some condition or activity experience the same or similar emotional reactions.

2. in twin studies, the presence of a given trait or disorder in both members of the pair. Evidence for genetic factors in the production of the trait or disorder comes from the comparison of concordance rates between identical and fraternal twins. Compare discordance.