diphthong

UK: /ˈdɪfθɒŋ/, /ˈdɪpθɒŋ/

US: /ˈdɪfθɔŋ, -θɑŋ, ˈdɪp-/

US: (dif′thông, -thong, dip′-)

WordReference Random House Learner's Dictionary of American English © 2025

diph•thong /ˈdɪfθɔŋ, -θɑŋ, ˈdɪp-/   n. [countable]

1. Phonetics a vowel sound that glides slightly from one sound to another but is considered to be a single sound, as the (oi) sound of toy or boil.
2. Linguistics (not in technical use)
   • a digraph, as the ea of meat.
   • a ligature, as æ.

WordReference Random House Unabridged Dictionary of American English © 2025

diph•thong  (dif′thông, -thong, dip′-), n. 

1. Phonetics an unsegmentable, gliding speech sound varying continuously in phonetic quality but held to be a single sound or phoneme and identified by its apparent beginning and ending sound, as the oi- sound of toy or boil.
2. Linguistics (not in technical use)
   • a digraph, as the ea of meat.
   • a ligature, as æ.

v.t., v.i. 

3. Phonetics to diphthongize.

• Greek díphthongos literally, having two sounds (di- di-¹ + phthóngos voice, sound)
• Late Latin diphthongus
• 1425–75; late Middle English diptonge

diph•thon•gal  (dif thông′gəl, -thong′-, dip-), diph•thon′gic, diph•thon′gous, adj. 

Collins Concise English Dictionary © HarperCollins Publishers::

diphthong / ˈdɪfθɒŋ ˈdɪp-/ noun

1. a vowel sound, occupying a single syllable, during the articulation of which the tongue moves from one position to another, causing a continual change in vowel quality, as in the pronunciation of a in English late, during which the tongue moves from the position of (e) towards ( ɪ )
2. a digraph or ligature representing a composite vowel such as this, as ou in mouth or æ in Cæsar

Etymology: 15th Century: from Late Latin diphthongus, from Greek diphthongos, from di-¹ + phthongos sound

diphˈthongal adjective