In traditional usage, the cult of a religion, quite apart from its sacred writings ("scriptures"), its theology or myths, or the personal faith of its believers, is the totality of external religious practice and observance, the neglect of which is the definition of impiety. Cult is literally the "care" owed to the god and the shrine. The term "cult" first appeared in English in 1617, derived from the French culte, meaning "worship" or "a particular form of worship" which in turn originated from the Latin word cultus meaning "care, cultivation, worship," originally "tended, cultivated," also the past participle of colere "to till"

By extension, "cult" has come to connote the total cultural aspects of a religion, as they are distinguished from others through change and individualization.

The meaning "devotion to a person or thing" is from 1829, and from that connotation comes the modern meaning of "cult" as in a "cultist" or a "cult following". Cult and cultist have recently accrued negative connotations that are separately dealt with at the entry cult.

Some Christians make refined distinctions between worship and veneration, both of which are outwardly expressed in cultus or cult and are indistinguishable to the observer. Catholicism and Eastern Orthodoxy distinguish between worship (Latin adoratio, Greek latreia [λατρεια]) which is due to God alone, and veneration (Latin veneratio, Greek doulia [δουλεια]), which may be lawfully offered to the saints. These private distinctions between deity and mediators are exhaustively treated at the entries for worship and veneration.

Among the observances in the cult of a deity are ritual, which may involve spoken or sung prayers or hymns, and often sacrifice, or substitutes for sacrifice. Other manifestations of the cult of a deity are the preservation of relics or the creation of images, such as icons (usually connoting a flat painted image) or three-dimensional cult images (the Judaeo-Christian "idols"), and the identification of sacred places, hilltops and mountains, fissures and caves, springs and pools, or groves, which may be the seat of an oracle. The sacred places may be elaborated by construction of shrines and temples, on which are centered public attention at religious festivals (called "Feasts" in some Christian communities) and which may become the center for pilgrimages.

The comparative study of cult practice is part of the disciplines of the anthropology of religion and the sociology of religion, two aspects of comparative religion.