Masturbation refers to the manual excitation of the sexual organs, most often to the point of orgasm. It can refer to excitation either by oneself or by another (mutual masturbation), but most commonly it is restricted to refer only to such activities performed by one's self. It is part of a larger set of activities known as autoeroticism, which also includes the use of sex toys and nongenital stimulation. Masturbation and coitus (sexual intercourse) are the two commonest sexual practices.
The term "masturbation" is from the Latin for "to defile with the hands". The word onanism is sometimes used as a synonym, but that word is rarely used today, especially since it originated in what is most likely a misinterpretation of the Biblical passage Genesis 38:7-9, in which Onan "spilled his seed (semen) upon the ground", now thought to be a reference to a practice of coitus interruptus.
The commonest technique of male masturbation is simple stroking of the penis.
Females commonly stroke or rub the vulva, especially the clitoris. Women may also use running water to stimulate the vulva. Some women enjoy stimulation of the vagina by inserting fingers or an object.
Members of both sexes may also masturbate by pressing or rubbing the genital area against an object, such as a pillow. Some persons of both sexes enjoy stimulation by inserting fingers or an object into the anus. Electric vibrators provide a strong stimulation of the penis or vulva/clitoris that many people enjoy, and may also be inserted into the vagina or anus.
Reading or viewing pornography, or sexual fantasy, are common adjuncts to masturbation.
Modern medicine recognizes that there is no significant long term harm caused by the practice of masturbation, and regards it as a normal practice. In past times some medical professionals taught that all sorts of deleterious effects could occur as a result of masturbation. Historically, many questionable "remedies" have been devised for masturbation, including physical restraint, electric shock, treating the genitalia with stinging nettles, and clitoridectomy.
In fact, both from the standpoint of avoiding unwanted pregnancy and that of avoiding sexually transmitted diseases, masturbation is the safest of sexual practices. Solitary masturbation carries no risk of pregnancy or sexually transmitted diseases. Masturbation with a partner (heterosexual) can result in pregnancy only if semen contacts the vulva. Masturbation with a partner (of any sex) can theoretically result in transmission of sexually transmitted disease by contact with semen or female sexual fluids, and such contact should be avoided with any partner whose disease-negative statues you aren't sure of. Objects inserted into the vagina or anus should be clean and of a kind that will not scratch or break, and care should be taken not to fully insert anything into the anus, as retrieval can require a visit to the emergency room.
Many conservative religious groups teach masturbation to be a sinful practice.
The Catechism of the Catholic Church, paragraph 2352, lists masturbation as one of the "Offenses Against Chastity" and calls it "an intrinsically and gravely disordered action" because "use of the sexual faculty, for whatever reason, outside of marriage is essentially contrary to its purpose." It goes on to caution that extenuating factors could exist, such as immaturity, habit, or psychological problems.