See nonoxynol-9

A method of pregnancy prevention in which a woman becomes familiar with her body and observes and charts various signs of fertility for several months, then abstains from vaginal intercourse during the fertile period. These signs are the basal body temperature (also known as waking temperature this is taken immediately upon awakening from sleep before any activity) and cervical fluid. Checking the position of the cervix is also helpful, but optional. In addition to these primary signs, as ovulation approaches a woman may experience secondary signs that may include abdominal bloating, pain or ache near an ovary, water retention, more acute senses (vision, smell and taste), swelling of the vulva and/or breast tenderness. NFP does not protect against HIV or other STIs. NFP is not as effective as other methods of birth control and relies heavily on observation, charting and abstinence from vaginal intercourse during a woman’s most fertile time. This method is not recommended for all women especially those that take medication that can alter cervical mucus, women who don’t have consistent monthly menstrual cycles and women whose temperature may not be accurate due to fever or other conditions. Women who are considering NFP and want to avoid pregnancy should talk with their OB/GYN to be certain this is a good method for them to use.

See natural family planning

A protrusion (or, less commonly, an inversion) located at the center of each breast, surrounded by the areola. The nipples of both sexes become erect during arousal and are commonly considered to be an erogenous zone. Stimulation of the nipples triggers the release of oxytocin. Women's nipples commonly express milk after childbirth. Polythelia refers to the presence of more than two nipples.

A type of sex toy designed to stimulate the nipples and/or breasts. Nipple toys may be used on men or women, as part of foreplay, intercourse, fantasy play or other types of sex play. Common types of nipple toys include clamps and vibrating devices.

A substance produced by the body that helps protect against heart disease and high blood pressure, and plays an important role in erection. Nitric oxide relaxes the arteries and blood vessels to improve blood flow, including to the penis. Drugs intended to treat erectile dysfunction, such as Cialis®, Levitra® and Viagra®, work to enhance nitric oxide's effect by inhibiting PDE-5.

(a.k.a., wet dream) An experience of male genital arousal, specifically an erection, while sleeping that results in the ejaculation of semen. Nocturnal emissions may result from sexual or non-sexual thoughts during a dream state. Women may experience orgasm during sleeping states as well, though these are less commonly described as nocturnal emissions.

(abbreviated N-9) A spermicide used for pregnancy prevention that is available in the form of jellies, foams, creams, films or suppositories. Many brands of condoms also contain N-9, and are labeled as spermicidally lubricated. N-9 offers no protection against STIs, and is thought to increase susceptibility particularly to HIV, as it can irritate the delicate membranes, particularly the vagina, cervix and rectum. If irritation of the vagina or penis occurs as a result of using N-9, it is best to stop using these products and use another method of birth control.

Transmission of information without the use of words, such as body language and other experience through the senses. Nonverbal communication plays an important role in attraction and flirting.