monophthong

[mon-uh f-thawng, -thong] /ˈmɒn əfˌθɔŋ, -ˌθɒŋ/
noun, Phonetics
1.
a vowel retaining the same quality throughout its duration.
Compare diphthong.
Origin
1610-20; < Greek monóphthongos equivalent to mono- mono- + phthóngos sound
Related forms
monophthongal
[mon-uh f-thawng-guh l, -thong-] /ˈmɒn əfˌθɔŋ gəl, -ˌθɒŋ-/ (Show IPA),
adjective
British Dictionary definitions for monophthong

monophthong

/ˈmɒnəfˌθɒŋ/
noun
1.
a simple or pure vowel
Derived Forms
monophthongal (ˌmɒnəfˈθɒŋɡəl) adjective
Word Origin
C17: from Greek monophthongos, from mono- + thongos sound