Peace describes a society or a relationship that is operating harmoniously and without violent conflict. Peace is commonly understood as the absence of hostility, or the existence of healthy or newly healed interpersonal or international relationships, safety in matters of social or economic welfare, the acknowledgment of equality and fairness in political relationships. In international relations, peacetime is the absence of any war or conflict. The study of peace also involves the causes for its absence or loss. These potential causes include: insecurity, social injustice, economic inequality, political and religious radicalism, and acute racism and nationalism. From the Anglo-Norman pas , and meaning "freedom from civil disorder", the English word came into use in various personal greetings from c.1300 as a translation of the biblical terms pax (from the Vulgate) and Greek eirene, which in turn were renderings of the Hebrew shalom. Shalom, cognate with the Arabic "salaam", has multiple meanings: safety, welfare, prosperity, security, fortune, friendliness. The personalized meaning is reflected in a nonviolent lifestyle, which also describes a relationship between any people characterized by respect, justice and goodwill. This latter understanding of peace can also pertain to an individual's sense of himself or herself, as to be "at peace" with one's own mind attested in Europe from c.1200. The early English term is also used in the sense of "quiet", reflecting a calm, serene, and meditative approach to the family or group relationships that avoids quarreling and seeks tranquility — an absence of disturbance or agitation.

In many languages the word for peace is also used a greeting or a farewell, for example the Hawaiian word Aloha, as well as the Arabic word Salam . In English the word peace is used as a farewell, especially for the dead as in Rest In Peace, RIP.