Sexual desire is an Emotion,motivational state, and an interest in sexual objects or activities, or as a wish, or drive to seek out sexual objects or to engage in sexual activities. Synonyms for sexual desire are libido and lust. Sexual desire is an aspect of a person’s sexuality, which varies significantly from one person to another, and also varies depending on circumstances at a particular time. Not every person experiences sexual desire; those who do not experience it may be labelled asexual. Sexual desire may be the single most common sexual event in the lives of people. Sexual desire is a subjective feeling state that can be triggered by both internal and external cues, and that may or may not result in overt sexual behaviour. Sexual desire can be aroused through imagination and sexual fantasies, or perceiving an individual whom one finds attractive. Sexual desire is also created and amplified through sexual tension, which is caused by sexual desire that has yet to be consummated. Sexual desire can be spontaneous or responsive. Sexual desire is dynamic, can either be positive or negative, and can vary in intensity depending on the desired object/person. The sexual desire spectrum is described by Stephen B. Levine as: aversion → disinclination → indifference → interest → need → passion.The production and use of sexual fantasy and thought is an important part of properly functioning sexual desire. Some physical manifestations of sexual desire in humans are; licking, sucking, puckering and touching the lips, as well as tongue protrusion.