Shoujo
: 少女 【しょうじょ】
(n.) daughter; young lady; virgin; maiden; little girl.
Should not be confused with shojou (書状) which means a letter or note, or shoujou (症状) which means the symptoms of a disease, or shojo (処女) which means specifically "virgin" (while shoujo can mean virgin, shojo only means virgin). However, it is commonly spelled as "shojo" due to romanization issues.
"Shoujo" is a demographic indicator for anime and manga aimed at girls. However, among Western fans, it is often misinterpreted to mean "an anime with the stylistic qualities usually associated with shoujo". In other words, shoujo is associated with a visual and storytelling style rather than with a demographic. While it is true that shoujo anime and manga traditionally tend to have a strong focus on relationships and character development, it is far too diverse to be pigeonholed so neatly. Weiss Kreuz, for example, could at first glance be mistaken for a shounen anime with its good guys fighting bad guys. But the emphasis on bishounen (as well as the hordes of female fans) make it clear that this is an anime aimed at girls, and therefore shoujo. And while some shoujo can be totally devoid of any true antagonism, other will feature soul-blithering drama.
There is a popular subgenre of shoujo called mahou shoujo, or "magical girl". While there are many subgenres of shoujo, this one is predominant enough to warrant a special mention. In said subgenre the heroines receive magical powers, usually for the purpose of fighting evil in the name of love and justice. Elaborate transformation sequences and cute costumes are a staple of magical girls. This subgenre also tends to feature more action than traditional shoujo.