Pronunciation of English ⟨wh⟩

The pronunciation of the digraph ⟨wh⟩ 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 ⟨w⟩, 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 ⟨wh⟩ in words like who and whom is now pronounced /h/. (A similar sound change occurred earlier in the word how.)

What is now English ⟨wh⟩ originated as the Proto-Indo-European consonant *kʷ (whose reflexes came to be written ⟨qu⟩ 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 symbol known as hwair; in Old English it was spelled as ⟨hw⟩. The spelling was changed to ⟨wh⟩ in Middle English, but the pronunciation remained [ʍ].

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