Monophthong
From Hull AWE
A monophthong - the word is pronounced with the stress on the first syllable, IPA: /'mɒ nəf ,θɒŋ/ - is a vowel sound which involves no movement of the tongue during its production - there is no glide, as there is in a diphthong.
McArthur (1998) says that "in RP there are 12 [monophthongs] (as in see, sit, set, hat, arm, got, saw, pull, pool, cup, fur, and the first syllable of ago)."
- The word monophthong is derived from Greek: μόνος (monos) 'single', 'one' and φθόγγος (phthongos) 'sound'.