Compassion is an emotion that evolved to facilitate cooperation and protect the weak and those who suffer. This review integrates three evolutionary arguments that converge on the hypothesis that compassion is a distinct affective experience. Empirical evidence reveals that compassion has distinct appraisal processes, signaling behaviors, and physiological responses that differentiate it from distress, sadness, and love. Compassion is associated with a desire to help others and is distinct from empathy, which is the vicarious experience of another's emotions. Compassion is also distinct from sympathy, which involves concern for someone considered inferior to the self. Compassion is a family of related states that center on concern for ameliorating the suffering of another individual. Empirical studies support this emotion-family approach to compassion and closely related states. Compassion is often grouped with sympathy and pity in lexical studies of emotion terms in English, Indonesian, Chinese, and Italian. Self-report studies also support the claim that compassion and sympathy are closely related. Compassion is a brief, context-specific response focused on a clear cause, and can develop into enduring sentiments. Emotional traits refer to general styles of emotional responses that persist across context and time. Compassion is a distinct affective state with a response profile that differs from those of distress, sadness, and love. Evolutionary analyses of compassion suggest that it evolved as a distinct affective state to facilitate cooperation and protect the weak. Compassion is also a desirable trait in mate selection processes and enables cooperative relations with non-kin. Compassion is a brief affective state associated with caregiving toward those who suffer or are in need. Compassion is also a trait-like tendency that can be influenced by individual differences in emotion regulation and self-efficacy. Compassion-related appraisals involve sensitivity to suffering, deservingness, and coping ability. Compassion is distinct from distress, sadness, and love in terms of its antecedent events and appraisal processes. Compassion-related display behavior includes facial and postural behaviors that signal commitment and cooperation. Nonverbal expressions of emotion serve several functions, including signaling intentions, motivations, and probable behaviors to others. Compassion is signaled in caregiving-related behaviors, including soothing vocalizations and tactile contact. Compassion-related facial and postural behavior includes concerned attention, such as furrowed eyebrows and forward head orientation, which differ from those that signal love. Compassion-related display behavior is distinct from those that signal love, which include Duchenne smiles, open-handed gestures, and forward leans. Compassion-related display behavior is also distinct from those that signal distress, which include raised eyebrows and nervous mouth movements. Compassion-related display behavior is a signal of commitment and cooperation, and is distinct from those that signal distress or love. Compassion is a distinct emotion that is associated with a desire to help others and is distinct from empathy, sympathy, and love. Compassion is also distinct from distress, sadness, and love in terms of its appraisal processes and physiological responses. Compassion isCompassion is an emotion that evolved to facilitate cooperation and protect the weak and those who suffer. This review integrates three evolutionary arguments that converge on the hypothesis that compassion is a distinct affective experience. Empirical evidence reveals that compassion has distinct appraisal processes, signaling behaviors, and physiological responses that differentiate it from distress, sadness, and love. Compassion is associated with a desire to help others and is distinct from empathy, which is the vicarious experience of another's emotions. Compassion is also distinct from sympathy, which involves concern for someone considered inferior to the self. Compassion is a family of related states that center on concern for ameliorating the suffering of another individual. Empirical studies support this emotion-family approach to compassion and closely related states. Compassion is often grouped with sympathy and pity in lexical studies of emotion terms in English, Indonesian, Chinese, and Italian. Self-report studies also support the claim that compassion and sympathy are closely related. Compassion is a brief, context-specific response focused on a clear cause, and can develop into enduring sentiments. Emotional traits refer to general styles of emotional responses that persist across context and time. Compassion is a distinct affective state with a response profile that differs from those of distress, sadness, and love. Evolutionary analyses of compassion suggest that it evolved as a distinct affective state to facilitate cooperation and protect the weak. Compassion is also a desirable trait in mate selection processes and enables cooperative relations with non-kin. Compassion is a brief affective state associated with caregiving toward those who suffer or are in need. Compassion is also a trait-like tendency that can be influenced by individual differences in emotion regulation and self-efficacy. Compassion-related appraisals involve sensitivity to suffering, deservingness, and coping ability. Compassion is distinct from distress, sadness, and love in terms of its antecedent events and appraisal processes. Compassion-related display behavior includes facial and postural behaviors that signal commitment and cooperation. Nonverbal expressions of emotion serve several functions, including signaling intentions, motivations, and probable behaviors to others. Compassion is signaled in caregiving-related behaviors, including soothing vocalizations and tactile contact. Compassion-related facial and postural behavior includes concerned attention, such as furrowed eyebrows and forward head orientation, which differ from those that signal love. Compassion-related display behavior is distinct from those that signal love, which include Duchenne smiles, open-handed gestures, and forward leans. Compassion-related display behavior is also distinct from those that signal distress, which include raised eyebrows and nervous mouth movements. Compassion-related display behavior is a signal of commitment and cooperation, and is distinct from those that signal distress or love. Compassion is a distinct emotion that is associated with a desire to help others and is distinct from empathy, sympathy, and love. Compassion is also distinct from distress, sadness, and love in terms of its appraisal processes and physiological responses. Compassion is