Imperial units commonly used units for length are (li), (tseung/cheung), (tsek/chek), (tsun/chun), (fen/fan) in descending scale order. These units are now rarely used in daily life, the imperial and metric systems being preferred. The imperial equivalents are written with the same basic Chinese characters as the Chinese system. In order to distinguish between the units of the two systems, the units can be prefixed with "Ying" () for the Imperial system and "Wa" () for the Chinese system. In writing, derived characters are often used, with an additional (mouth) radical to the left of the original Chinese character, for writing imperial units.
Imperial Valley and to the south the international boundary with the U.S. state of California and Baja California. The culture of the area blends those of the United States and Mexico, due to its regional history and geographic location along the international border. The Imperial Valley economy is based on agriculture. Imperial Valley was so named by the Imperial Land Company, in hopes of attracting settlers. Having done that it is now the home of the El Centro metropolitan area and also an economic center of California's government defined "South Border". Locally, the terms "Imperial Valley" and "Imperial County" are used synonymously.