Compassion motivates people to go out of their way to relieve the physical, mental, or emotional pains of others and themselves. Compassion is often regarded as being sensitive to the emotional aspects of the suffering of others. When based on notions such as fairness, justice, and interdependence, it may be considered rational in nature.

The word "compassion" comes from Middle English, and derives from Old French, via ecclesiastical Latin compassio(n- ), from compati (‘to suffer with’).

Compassion involves "feeling for another" and is a precursor to empathy, the "feeling as another" capacity (as opposed to sympathy, the "feeling towards another"). In common parlance, active compassion is the desire to alleviate another's suffering.

Compassion involves allowing ourselves to be moved by suffering, and experiencing the motivation to help alleviate and prevent it. An act of compassion is defined by its helpfulness. Qualities of compassion are patience and wisdom; kindness and perseverance; warmth and resolve. It is often, though not inevitably, the key component in what manifests in the social context as altruism. Expression of compassion is prone to be hierarchical, paternalistic, and controlling in responses. The difference between sympathy and compassion is that the former responds to others' suffering with sorrow and concern whereas the latter responds with warmth and care. An article by the Clinical Psychology Review suggests that "compassion consists of three facets: noticing, feeling, and responding."

The English noun compassion, meaning to suffer together with, comes from Latin. Its prefix com- comes directly from com, an archaic version of the Latin preposition and affix cum (= with); the -passion segment is derived from passus, past participle of the deponent verb patior, patī, passus sum. Compassion is thus related in origin, form and meaning to the English noun patient (= one who suffers), from patiens, present participle of the same patior, and is akin to the Greek verb πάσχειν (= paskhein, to suffer) and to its cognate noun πάθος (= pathos). Ranked a great virtue in numerous philosophies, compassion is considered in almost all the major religious traditions as among the greatest of virtues.