The penis is the male organ of copulation, attached to the groin, homologous with the clitoris. It is also the male organ of urinary excretion.
The penis is designed for insertion into the vagina and nature's intention for copulation is reproduction. As such, measures such as the wearing of condoms are necessary to avoid pregnancy.
Because it typically has a man's most excitable erogenous zone, it is an area concentrated on by both him and his sexual partner.
When a male is sexually aroused, the three areas of erectile tissue will usually fill with blood and his penis will expand and stiffen. The penis will often move more upward than in the flaccid (non-erected) state, but the angle varies between males and is no indication of the height of arousal. (A penis can also become erect without the man being aroused.)
The primary body modification made to the penis is circumcision; during this process, the foreskin is cut away such that the head of the penis is always exposed. A far less common, but popular enough in BDSM and sexually-interested cultures, is piercing of the head of the penis for insertion of a bar or ring.
Because penises vary in size, it is important when buying any device or toy that fits onto the penis to ensure that it will fit without damage. Some toys can do a great deal of harm or, at the least, cause unintentional embarrassment. [ http://english.pravda.ru/fun/2002/06/20/30796.html ]
- Also see the page [ Sex organs ]