Concept
The pronunciation of the digraph in English has changed over time, and still varies today between different regions and accents. It is now most commonly pronounced /w/, the same as a plain initial , although some dialects, particularly those of Scotland, Ireland, and the Southern United States, retain the traditional pronunciation /hw/, generally realized as ʍ, a voiceless "w" sound. The process by which the historical /hw/ has become /w/ in most modern varieties of English is called the wine–whine merger. It is also referred to as glide cluster reduction. Before rounded vowels, a different reduction process took place in Middle English, as a result of which the in words like who and whom is now pronounced /h/. (A similar sound change occurred earlier in the word how.) What is now English originated as the Proto-Indo-European consonant *kw (whose reflexes came to be written in Latin and the Romance languages). In the Germanic languages, in accordance with Grimm's Law, Indo-European voiceless stops became voiceless fricatives in most environments. Thus the labialized velar stop *kw initially became presumably a labialized velar fricative *xw in pre-Proto-Germanic, then probably becoming *[ʍ] – a voiceless labio-velar approximant – in Proto-Germanic proper. The sound was used in Gothic and represented by the letter hwair. In Old High German, it was written as , a spelling also used in Old English along with (using the letter wynn). In Middle English the spelling was changed to (with the development of the letter ) and then , but the pronunciation remained [ʍ]. Because Proto-Indo-European interrogative words typically began with *kw, English interrogative words (such as who, which, what, when, where) typically begin with (for the word how, see below). As a result, such words are often called wh-words, and questions formed from them are called wh-questions. In reference to this English order, a common cross-lingual grammatical phenomenon affecting interrogative words is called wh-movement.