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. (june 2019)
american english pronunciation of no highway cowboys
, showing five diphthongs: /
a diphthong (/ dif-thong or / dip-thong; from greek: δίφθονγος, diphthongos, literally "double sound" or "double tone"), also known as a gliding vowel, is a combination of two adjacent vowel sounds within the same syllable. technically, a diphthong is a vowel with two different targets: that is, the tongue (and/or other parts of the speech apparatus) moves during the pronunciation of the vowel. in most varieties of english, the phrase no highway cowboys / has five distinct diphthongs, one in every syllable.
diphthongs contrast with monophthongs, where the tongue or other speech organs do not move and the syllable contains only a single vowel sound. for instance, in english, the word ah is spoken as a monophthong (/), while the word ow is spoken as a diphthong in most varieties (/). where two adjacent vowel sounds occur in different syllables—for example, in the english word re-elect—the result is described as hiatus, not as a diphthong. (the english word hiatus / is itself an example of both hiatus and diphthongs.)
diphthongs often form when separate vowels are run together in rapid speech during a conversation. however, there are also unitary diphthongs, as in the english examples above, which are heard by listeners as single-vowel sounds (phonemes).