Why Does です Sound Like “Dess”? Devoiced Vowels in Japanese

です often sounds like “dess” because the final u is devoiced. In Japanese, the vowels i and u often lose their voice when they sit between two voiceless consonants, or follow a voiceless consonant at the end of a sentence. The vowel is still pronounced, but your vocal cords do not vibrate, so it sounds whispered or almost missing. The same thing makes すき (suki, “like”) sound close to “ski” and ます (masu) close to “mass.” The spelling does not change: it is still です in kana and desu in romaji.

What vowel devoicing is

The Tokyo University of Foreign Studies (TUFS) module on vowel devoicing describes it this way: when i and u come between voiceless consonants, or follow a voiceless consonant at the end of a sentence, the vocal cords do not vibrate, so the vowel can be hard to hear. The module says the su in です and in the ます verb ending is usually devoiced.

Notice what that does and does not say. The vowel is not deleted from the word; it is said without voice. That is why a whisper of the u is closer to the target than cutting it off with a hard “s.”

When it happens

Between voiceless consonants

TUFS lists the consonants of the か, さ, た, は and ぱ rows as voiceless. In romaji, that means k, s, sh, t, ch, ts, h, f and p. When an i or u sits between two of them, expect it to fade. The TUFS examples:

• すき 好き (suki), “like”: the u sits between s and k
• きく 聞く (kiku), “to listen”: the first i sits between k and k
• くつ 靴 (kutsu), “shoes”
• つき 月 (tsuki), “moon”
• した 下 (shita), “below”
• きかい 機会 (kikai), “chance”

At the end of a sentence

TUFS says devoicing also happens easily at the end of a sentence. This applies when the i or u follows a voiceless consonant, as in す and き. That is the です and ます case: がくせいです。 (gakusei desu, “I am a student.”) ends in a whispered u, and so does いきます。 (ikimasu, “I go.”).

When it does not happen

The TUFS practice page pairs words where one devoices and the other does not. In each pair, the second word has a voiced sound, such as m, r, g or n, after the vowel:

• がくせい 学生 (gakusei, “student”) vs がくもん 学問 (gakumon, “learning”)
• きく 聞く (kiku, “to listen”) vs きる 着る (kiru, “to wear”)
• つき 月 (tsuki, “moon”) vs つぎ 次 (tsugi, “next”)
• あき 秋 (aki, “autumn”) said alone vs あきになる (aki ni naru, “it becomes autumn”)
• バス (basu, “bus”) said alone vs バスが来た (basu ga kita, “the bus came”)

The last two pairs show that the same word can change. あき ends a sentence when said alone, so its i fades. Add に after it and the i is no longer at the end.

The modules describe this pattern for i and u only.

A tendency, not a spelling rule

The TUFS wording is careful: vowels “may not be easily heard,” and devoicing happens easily rather than always. Treat it as a pattern to expect, not a rule you must apply to every word. Two practical uses follow from that:

• Listening. When you hear something like “s'ki” or “ts'ki,” check whether a word with すき or つき fits.
• Speaking. As advice, avoid stressing the u in です as a full, voiced “su.” A light, whispered u is closer to the pattern TUFS describes.

Devoicing is separate from pitch accent, which is about high and low pitch across a word. See Japanese pitch accent for that topic. For counting beats in a word, see how to remember a Japanese word's pronunciation.

Practice with three starter words

Inku's free browser flashcards include a JLPT N5 starter deck with three words that fit the pattern: 学生 (がくせい, gakusei), 月 (つき, tsuki) and 人 (ひと, hito). In each, an i or u sits between voiceless consonants. When one comes up, say it with that vowel whispered: ga-k(u)-sei, ts(u)-ki, h(i)-to. Then tap Hear it, which uses your device's Japanese voice if it has one. Device voices vary, so treat it as a rough check. If the voice reads a different word, use the TUFS recordings. The deck needs no account, and its progress stays in your browser.

Sources

• TUFS Language Modules: Vowel Devoicing — i and u between voiceless consonants or at sentence end are said without vocal cord vibration; ka, sa, ta, ha, pa columns are voiceless; examples suki, kiku, kutsu, tsuki, kikai; the su of desu and masu is usually devoiced. (checked 2026-10-16)
• TUFS Language Modules: Devoiced Vowels — Vowels 'may not be easily heard'; examples suki, kiku, kusa, tsuki, shita. (checked 2026-10-16)
• TUFS Language Modules: Devoiced Vowels, practice and answers — Pairs 学生/学問, 着る/聞く, 次/月, あき/あきになる, バス/バスが来た; answers on the next page (03-03-03) mark 学生, 聞く, 月, あき and バス as devoiced. (checked 2026-10-16)
• Inku: Free Japanese flashcards — Free browser flashcards with a JLPT N5 starter deck containing 学生 がくせい, 月 つき and 人 ひと; Hear it uses the device's Japanese voice; no account; progress saved in the browser. (checked 2026-10-16)

Prepared by our editorial team with AI assistance. Product details are checked against the sources below.

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