Semiotics (from the Greek word σημεῖον semeion, meaning “sign”) is the discipline that studies signs and how they make sense (signification). A sign is generally something that refers to something else (for medieval philosophers aliquid stat pro aliquo), and semiotics is the discipline that studies the phenomena of signification. Signification means any relation that links something materially present to something else absent (the red light on a traffic light means “stop”). Whenever a signification relation is enacted or used, a communication process is triggered (the traffic light is red, so the “sign” of the lit red light communicates to the driver to stop the car). Meaning relations define the system that comes to be presupposed by concrete communication processes.