ablution: ritual washing typically related to purification.

aboriginal: original or early inhabitant; indigenous; native groups, animals, or plants.

aesthetics: the study of beauty; sometimes used for the formal study of artistic judgment.

agnostic: one who neither believes in God nor claims that God does not exist, but instead emphasizes that the existence and nature of  God are unknown.

allegory: typically a symbolic tale or image, whose meanings are hidden behind the literal, face-value interpretation.

altruism: possessing a concern for other beings over and above one’s personal welfare.

ancestor worship: religious actions that are concerned with venerating or appeasing spirits of dead relatives.

animism: belief that features of the natural world, such as particular plants, lakes, mountains, animals, persons, and such, are abodes of spirits or souls.

anthropology: (anthropos – human being + logos – study); social science that concerns itself with the study of human beings; now primarily focussed on social organization and culture.

anthropomorphic: representation of gods with human characteristics or form.

anthropotheism: belief that gods are merely humans who have been elevated to divine status.

apeiron: Greek term for a single, undifferentiated, and subtle essence, which is the source of all things, and to which all things return.

apocalyptic: concerning the end of the world including prophesies of catastrophic destruction; sometimes also concerns final judgment.

apocrypha: mostly texts, whose authenticity are in doubt.

apologetics: a branch of theology that seeks to justify the doctrines of a particular faith through formal arguments.

apologist: defender or advocate for a particular religious tradition, belief, or view.

apostasy: rejection of the faith that one once held.

appease: to pacify, propitiate, relieve, or satisfy; often refers to sacrifice, offerings, praise, and rituals designed a pacify a god or spirit in order to avoid harm.

archetype: in Jungian psychology, a mental image and universal prototype inherited from ancient humans and found in the collective unconscious.

asceticism: the practice of self-denial and austerity; often a feature of disciplines concerned with the purification of one’s spirit or soul.

atheist: one who does not believe in the existence of any supernatural divine entity.

autochthonous: see indigenous.

avatar: manifestation or incarnation of a deity, especially in Hinduism.