I just finished with a pronunciation class, so this is on my mind. I’m sure most of you don’t care, but humor me, eh? 😃

Japanese learners quickly discover that English vowels are not their friends. In fact, the difference between あ・い・う・え・お and English “a e i o u” is so deep it practically creates two different acoustic worlds. This gap alone explains most of the “Japanese accent” when speaking English, far more than grammar or consonants ever do, even far more than the th or r/l problem that most people waste so much time focusing on.

The Japanese Vowel System Is Shockingly Simple

Japanese has five vowels, and each one is:

• Pure (a single, steady sound)
• Short (roughly one beat)
• Flat in intonation (the pitch moves on the word, not inside the vowel)
• Stable (no changing mouth shape once the vowel begins)

These five:

あ・い・う・え・お
a / i / u / e / o

• pronounced as in Spanish or Italian, roughly: ah, ee, oo, eh, oh. But keep them short, shorter than you will likely read those pronunciations I just wrote.

They are textbook “monophthongs” — clean, unmoving sounds. You open your mouth to the right shape and hold it. Nothing twists or slides.

To a Japanese speaker, this is obvious. To an English speaker, this is exotic.

English Vowels Are… Not That

English has the same letters, but not the same vowels. In fact, English doesn’t have five vowel sounds; it has somewhere between 14 and 20, depending on the dialect.

And in American English specifically, the vowels you think are simple are almost always diphthongs—sounds that slide from one position to another.

To keep it simple, let’s just look at the vowel names English speakers say when reading the list.

Examples:

• “A” → /eɪ/ (ay)
• “I” → /aɪ/ (eye)
• “O” → /oʊ/ (oh)
• “U” → often /juː/ (yuu)

Notice the shape change embedded inside each vowel. There is movement, tension, and length. The vowel itself carries meaning. Stress changes the pitch. Duration changes the word.

Compare a Japanese o to an English “oh”:

• Japanese: o (one clean hit, done)
• English: oʊ (begins closed, opens, slides upward, stretches)

I didn’t forget “E”. The English vowel name /iː/ is almost the same shape as Japanese い, but longer and tenser.

That stretch for o and e can be nearly double the Japanese vowel length. To Japanese ears, English vowels are elastic; to English ears, Japanese vowels are clipped.

Why This Creates the “Japanese Accent”

When Japanese speakers apply Japanese vowel rules to English, three predictable things happen.

1. English diphthongs get flattened

“say” becomes closer to “seh”.
“go” becomes closer to “go” (but without the “ou” glide). “go” with what sounds like a clipped o to English speakers, versus “gou/goh” with a more extended o that might include some pitch or intonation change.

Perfectly logical, of course. Japanese vowels don’t move. English ones do.

2. English long vowels get shortened

Native Japanese timing cuts vowels to one beat.
But in English, vowel length marks differences:

• “beat” vs “bit”
• “seat” vs “sit”
• “fool” vs “full”

Shortening the vowel collapses the contrast and turns the first word above into the second (reading that i in the Japanese way, as a short ee sound).

3. The pitch stays flat inside the vowel

English moves pitch inside the vowel sound.
Japanese moves pitch between vowels.

So when Japanese learners maintain a flat vowel, English listeners often mis-parse the emotional tone, the emphasis, or even the meaning.

All of this happens even with perfectly correct grammar.

The Accent Isn’t About Consonants, It’s About Timing and Purity

Consonants matter, but vowels shape the music of a language. Japanese is a mora-timed language: steady, even beats. English is stress-timed: elastic rhythm, long vowels, short vowels, reductions, stress waves.

When a Japanese speaker brings Japanese vowel habits into English, the entire rhythm shifts. It’s not “wrong”; it’s simply a different operating system.

And because vowels carry the emotional weight in English, the result can feel dramatic to native listeners—much more so than mispronouncing th as s or swapping l and r.

Why Understanding This Helps Learners

Most Japanese learners try to memorize word lists, but they rarely get explicit training on vowel behavior. Yet fixing vowels is the single fastest way to sound clearer and more natural in English.

The crucial lesson:

English vowels aren’t just sounds.
They’re movements.

Once you accept that, English pronunciation becomes far less mysterious, and far less frustrating.

Now… just to be fair, the exact same thing happens in reverse to Americans trying to speak Japanese. We have a devil of a time getting the vowels right, and our English intonation tends to wreck Japanese pitch accent.

Anyway, so now you know, and knowing is half the battle.

❦

David is an American teacher and translator lost in Japan, trying to capture the beauty of this country one photo at a time and searching for the perfect haiku. He blogs here and at laspina.org. Write him on Bluesky. 【Support @dbooster with Hive SBI】