In most English words the digraph at the beginning of a word or syllable and followed by a vowel represents the voiced dental fricative /ð/ (this, that, another), or when the digraph is preceded or followed by a consonant it represents the voiceless fricative /?/ (through, thwart, baths, earth). In a few words can be silent /Ø/ (asthma).
The digraph in most dialects of English is pronounced as the labio-velar approximant /w/ (what, which, why) or, as the voiceless glottal fricative /h/ (who). Several words evolved from Old English that were originally spelled with the cluster had undergone a spelling change (hw ? wh). In some dialects, for many of those words, the sound /hw/ has been retained.
The diagraph , especially at the beginning of words, most often denotes the cluster /kw/ (quick, queen, squat), but may also represents the voiceless velar stop /k/ (croquet, toque). Some loanwords have entered English where the q is not followed by a u. For those of Turkish, Persian or Arabic origin the letter often represents the voiceless velar stop or plosive /k/ (qabal, qat, qindar); and for those of Chinese origin the letter often represents the voiceless palato-alveolar affricative /t?/ (qi, qigong, qin).