Shōnen (少年), commonly spelled shounen, is a Japanese word usually translated as "young boy", although it is commonly used to refer to males of up to high-school age as well. The word is composed of the characters meaning "few" and "year[s]". The word can also mean "pure of heart". In English, it usually refers to anime and manga which is primarily intended for boys, although there can be crossover appeal to girls as well. Some popular examples are Mobile Suit Gundam, Dragon Ball, and Fist of the North Star.
Shōnen anime and manga is characterized by high-action, often humorous plots featuring male protagonists. The camaraderie between boys or men on sports teams, fighting squads, etc. is often emphasized. Unrealistically attractive female characters are also common (see fanservice), but are not a requirement—Dragon Ball Z for example has only a few unremarkable female characters. The art style of shōnen also tends to be less flowery than that of shōjo, although there is significant variability by artist.
In contrast to shōnen, anime and manga for men (college age and up) is called seinen. Despite a number of significant differences, many Western fans don't make a distinction between shōnen and seinen. This is due to the fact that very few seinen manga have been published outside of Japan. On the other hand, many older men in Japan read shōnen magazines because of their ease of reading during commutes to and from work on trains. Consequently shōnen magazines (including Shonen Jump) are the most popular manga magazines in Japan.
Several series have notorious female audiences, who predominantly included them in non-canonical yaoi (and even shota-con) fanwork and dōjinshi.
Also see shōjo—anime and manga intended for girls, josei—anime and manga intended for adult women, and seinen—anime and manga intended for adult men.
The most obvious and common example of shounen is "fighting" anime, where extremely powerful warriors duke it out amongst each other with various forms of martial arts and superpowers.
Other examples of non-fighting shounen anime are the sports anime like Initial D that are starting to make an impact in the West.
Above violence or combat, one could say the overarching characteristic of shounen anime is a fast-paced story where action and adrenalin are privileged over plot.
Shounen anime is one of the most popular sub-genres of the anime medium, and is easily one of the big factors in anime's rise in Japan from the time of World War II to today.
Shounen anime stories are more often than not action-packed, fast paced, and focus on such items as violence, power, and stunning visuals.
Shounen's focus on action and its prominent, heroic characters makes it some of the most well-liked and popular types of anime that's out there.