Astrology (from Greek: αστήρ, αστρός (astér, astrós), "star", and λόγος, λόγου (lógos, lógou), "word" or "speech" lit. to talk about the stars) is a group of systems, traditions, and beliefs in which knowledge of the relative positions of celestial bodies and related details is held to be useful in understanding, interpreting, and organizing information about personality, human affairs, and other terrestrial matters. A practitioner of astrology is called an astrologer, or, less often, an astrologist. Numerous traditions and applications employing astrological concepts have arisen since its earliest recorded beginnings in the 2nd millennium BCE. It has played a role in the shaping of culture, early astronomy, and other disciplines throughout history.