The kilometre per hour (American English: kilometer per hour) is a unit of both spee (scalar) and velocity (vector). The unit symbol is km/h or km·h−1; however, the colloquial abbreviations "kph" and "kmph" are sometimes also used in English-speaking countries, in analogy to mph, although these are not in accordance with international scientific standards. In North American slang and military usage, km/h (as well as km) is commonly pronounced, and sometimes even written, as klicks or kays (K's), although these may also be used to refer to kilometres.