What does monophthong mean?
A monophthong is a vowel sound whose articulation remains essentially fixed from beginning to end. Unlike a diphthong, which moves from one vowel position toward another, a monophthong is heard as a single, stable vowel quality. The term is especially important in phonetics and phonology, where vowel systems are described according to the number and degree of articulatory movements involved in each sound. Many English vowel sounds, including those in words such as “cat,” “see,” and “cup,” are treated as monophthongs, while the vowel sequences in “boy,” “day,” and “go” are commonly classified as diphthongs. The distinction is not always straightforward, because speakers differ in how clearly they articulate the onset and off-glide of a vowel, and phonetic analysts may describe the same vowel differently. Nevertheless, understanding monophthongs is essential for describing pronunciation, comparing dialects, teaching pronunciation, and analyzing historical changes in the sounds of language.
nounA vowel sound produced with a single, stable vocal-tract position throughout its duration. In phonetics, it contrasts with a diphthong, in which the articulatory position changes noticeably during the vowel.
- A vowel sound characterized by one stable articulation and one principal resonance, without the internal glide characteristic of a diphthong.
"The vowel in the English word “cat” is a monophthong, whereas the vowel sequence in “boy” contains a diphthong."
"The phoneme /ɪ/ in “sit” is generally analyzed as a monophthong in contemporary English."
"Historical vowel changes can turn an earlier diphthong into a monophthong in a particular language."
The plural is used when discussing individual vowel sounds or comparing them across languages and dialects.
"The dialects differ in how many monophthongs they use."
Most English vowels are monophthongs, but the diphthongs in words such as “boy,” “day,” and “go” hide tiny journeys inside a single syllable.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of monophthong
The word was formed in the 19th century from Greek roots meaning “one” and “sound,” following the established term diphthong. Monophthong comes from the combining form mono- and the Greek noun phthongos, “sound,” which also underlies phthong and the related terms triphthong and diphthong. Its name reflects the defining contrast: a monophthong has one vowel position, while a diphthong has two and a triphthong has three.
Related word forms
How monophthong is actually used
This is primarily a specialist term used in phonetics, phonology, linguistics, and language teaching. It is also encountered in discussions of sound change, vowel inventories, and dialect differences.
Easily confused with monophthong
A monophthong is a single vowel quality, while a diphthong involves a perceptible glide from one vowel position to another within one syllable.
A monophthong remains at one vocal-tract position, whereas a triphthong moves through three distinct vowel positions during a single syllable.