| Term | Definition |
| sexual response cycle | The four stages of sexual responding described by Masters and Johnson - excitement, plateau, orgasm, and resolution. |
| refractory period | A resting period after orgasm, during which a man cannot achieve another orgasm. |
| sexual disorder | A problem that consistently impairs sexual arousal or functioning. |
| estrogen | A sex hormone, secreted in greater amounts by females than by males. In nonhuman female mammals, estrogen levels peak during ovulation, promoting sexual receptivity. |
| testosterone | The most important of the male sex hormones. Both males and females have it, but the additional testosterone in males stimulates the growth of the male sex organs in the fetus and the development of the male sex characteristics during puberty. |
| sexual orientation | An enduring sexual attraction toward members of either one's own sex (homosexual orientation) or the other sex (heterosexual orientation). |