A taxis (plural taxes , from the Ancient Greek , meaning "arrangement") is the movement of an organism in response to a stimulus such as light or the presence of food. Taxes are innate behavioral responses. A taxis differs from a tropism (turning response, often growth towards or away from a stimulus) in that the organism has motility and demonstrates guided movement towards or away from the stimulus source. It is sometimes distinguished from a kinesis, a non-directional change in activity in response to a stimulus.