/ ˈmɒnəfθɒŋ; NAmE ˈmɑːnəfθɑːŋ; ˈmɑːnəθ-/ noun
( phonetics ) a speech sound that consists of only one vowel sound, for example the sound /u:/ in queue /kju:/
—compare diphthong , triphthong
► mono·ph·thong·al / ˌmɒnəfˈθɒŋl; NAmE ˌmɑːnəfˈθɑːŋl; ˌmɑːnəˈθ-/ adjective
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WORD ORIGIN
early 17th cent.: from Greek monophthongos , from monos single + phthongos sound.