wh

Wh is a two-letter combination that can refer to two distinct concepts in English-language contexts. First, in orthography, wh denotes a digraph used in English to form a class of interrogative and relative words such as who, what, when, where, why, and which. The spelling traces to Old English hw- and to Proto-Germanic *hwi-, representing a labial-velar onset that was once pronounced as /hw/ or as /ʍ/ in some dialects. In many modern dialects, especially in North American and some British varieties, the distinction between /hw/ and /w/ has merged, so words like which and witch can be homophonous in those dialects. The usage and pronunciation vary by dialect and history, and some languages retain a distinct /hw/ sound.

Second, Wh is the symbol for watt-hour, a unit of energy equal to one watt sustained for one hour. It is a derived unit used in practical electricity contexts. One Wh equals 3600 joules. The kilowatt-hour (kWh) is the more common unit for measuring household energy consumption; 1 kWh equals 1000 Wh and equals 3.6 million joules. The Wh is widely used on energy bills and in equipment specifications, but for scientific purposes joules are typically preferred, with conversions to larger multiples as needed.

Other uses include abbreviations such as WH for White House in official shorthand or as an acronym for various organizations; context determines meaning.