Translation guide
A diphthong is a complex vowel sound that begins with one vowel and glides into another within the same syllable. Japanese has relatively few true diphthongs compared to English, and many apparent vowel sequences are actually separate syllables (hiatus). This guide explains how to understand and produce Japanese diphthong-like sequences.
The learner wants to know what a diphthong is in the context of Japanese and how to recognize or produce them.
In Japanese, sequences like 'ai' or 'oi' are usually pronounced as two distinct vowel sounds in separate morae (timing units), not as a single gliding sound. For example, あい (ai) is two beats, not a diphthong like English 'eye'. True diphthongs are rare and mostly occur in loanwords or as allophones in fast speech.
love (two morae: a-i)
carp (two morae: ko-i)
The linguistic term for 'diphthong' in Japanese. Used in academic or technical contexts.
Japanese has few diphthongs.
Another term for vowel sequences, sometimes used to describe diphthong-like combinations. Less common than 二重母音.
An example of a vowel sequence is 'ai'.
The learner wants to pronounce Japanese vowel combinations naturally, especially those that resemble English diphthongs.
Unlike English diphthongs where the first vowel is longer and glides into the second, Japanese vowel sequences are pronounced with each vowel given a full mora. Avoid reducing the second vowel. For example, say 'ah-ee' for あい, not 'eye'.
ai (two distinct vowels)
oi (two distinct vowels)
In casual or rapid speech, vowels may glide a bit, but the rhythm remains two beats. Do not intentionally create a diphthong; let it happen naturally if at all.
amazing (often pronounced quickly, but still su-go-i)
The learner wants to know which Japanese sound combinations are often perceived as diphthongs by English speakers.
The sequence 'ai' is two morae. It appears in many words and is not a diphthong.
The sequence 'oi' is two morae. Not like English 'oy'.
The sequence 'ui' is two morae. Often found in words like うい (first) or さむい (cold).
The sequence 'ei' is often pronounced as a long 'e' sound (ええ) in many dialects, but in careful speech it is two morae. In standard Japanese, it is usually a long vowel, not a diphthong.
The learner wants to know how English diphthongs are represented in Japanese loanwords.
For example, English 'cake' (with diphthong /eɪ/) becomes ケーキ (keeki) with a long vowel. English 'boy' (/ɔɪ/) becomes ボーイ (booi) with two vowels. The glide is often lost or replaced by a long vowel.
mail (long vowel instead of diphthong)
delicious
cold (weather)
teacher (often pronounced sensee)