Chinese martial arts, colloquially referred to as kung fu or gung fu (Chinese: 功夫; pinyin: gōngfu) and wushu (simplified Chinese: 武術; traditional Chinese: 武術; pinyin: wǔshù), are a number of fighting styles that have developed over the centuries in China. These fighting styles are often classified according to common traits, identified as "families" (家; jiā), "sects" (派; pài) or "schools" (門, mén) of martial arts. Examples of such traits include physical exercises involving animal mimicry, or training methods inspired by Chinese philosophies, religions and legends. Styles that focus on qi manipulation are called internal (内家拳; nèijiāquán), while others that concentrate on improving muscle and cardiovascular fitness are called "external" (外家拳; wàijiāquán). Geographical association, as in northern (北拳; běiquán) and "southern" (南拳; nánquán), is another popular classification method.