In several sources it's mentioned that a SMALL TSU doubles consonants.

My problem is, some websites give almost identical examples with:

っ/ッ + (S, T, C, K, G, B, P)

But what about the others?:

っ/ッ + (M, N, V, W ...)

When I use some online converter(Kana>Romaji), they double all of them.

So, does a SMALL TSU double all consonants or not? And if not, in which cases?

Thank you for your help!


A small tsu (sokuon) geminates (doubles) the following consonant. In native vocabulary, only unvoiced consonants can be geminated. This includes the さ, た, か, and ぱ rows. A double n as in おんな is not really pronounced the same way as *おっな would be if it were a word.

In loanwords that require gemination of other consonants, N tends to use ン, M uses ン or ム, W uses ウ, and others use the -u form of their row. Some examples are:

  • homemade → ホームメード
  • comma → コンマ
  • whistleblower → ホイッスルブロウワー
  • role-playing game → ロウルプレイングゲーム

Some loanwords do use the sokuon where native words would not, such as:

  • big → ビッグ
  • badge → バッジ

The important thing is that these are all loanwords. You generally won't see such examples written in hiragana, though the sokuon is used the same way in either writing system.

You may also see the small tsu at the end of a word or sentence. There it represents a glottal stop, an abrupt ending.

  • Nice answer. Maybe you could add some examples, especially in your second paragraph. – Earthliŋ Jan 5 '17 at 8:51
  • I agree, some examples would be nice. You say, only unvoiced consonants can be geminated. Does this apply to Hiragana and Katakana? And what is with the Z- and Y-row? Does it double or not? – Pii83 Jan 5 '17 at 9:32
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    The ざ row is voiced, so won't geminate in any native words. Examples of gemination in semivowels like Y and W are extremely hard to find, at least for me. I would expect や to take い in the same way that わ takes う. – Fox Jan 5 '17 at 10:01
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    P is unvoiced. This site elearnenglishlanguage.com/blog/learn-english/pronunciation/… is geared toward English-learning, but it has a nice description of what distinguishes voiced from unvoiced consonants. – Fox Jan 14 '17 at 4:31
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    There's also the odd geminate //h// in borrowed バッハ (Bach). There's also sometimes a っ between vowels, not just at the end, but similarly used to indicate a glottal stop. This doesn't happen so much in Japanese, but may appear in borrowings from languages that do have this, like Hawaiian: ハワッイ is a closer phonetic match to Hawaiian //haβaʔi//. – Eiríkr Útlendi Dec 14 '20 at 18:15

For one thing, [v] is not a legitimate consonant in native Japanese. You may see it used in loanwords, but the pronunciation varies between speakers; some native speakers, especially younger generations, pronounce it as a [v], but some people still pronounce it as a [b], which is what has historically been used in Japanese to approximate a [v] sound. So it falls into the same category as [b].

For M, っ is not used; instead a ん is used preceding it; so "hammer" is written as ハンマー, not *ハッマー. This is also the case for N. As for W, there are no native words (that I'm aware of) that use a geminate [w] sound, and I actually can't think of a word in any language that would end up being transcribed in such a way that you would need to, but I suppose it wouldn't be incorrect to use a っ with it.


Tom Kelly's response is downvoted, but is actually more correct than any other phonologically speaking, but still not the entire story so I'll elaborate on it and will show an audio analysis comparing it with true gemination so that the difference be visible.

The sokuon in Japanese maps to what Japanese speakers perceive as a coherent atomic unit of sound [phoneme] which is probably why it is written with a single symbol — the Japanese do not consider it merely an orthographical quirk but an actual consonant of Japanese. Such a phoneme is called an archiphoneme, a rare type of phoneme that lacks a consistent underlying place and method of articulation. That is to say that Japanese speakers perceive it as it's own consonant, but it has no meaningful way to be pronounced in isolation. /k/ as in the start of “coal” is a phoneme in English, but English speakers can pronounce it in isolation on command. Archiphonemes are indeed quite rare in languages, and English lacks them entirely. This phoneme is conventionally denoted as /Q/ with a capital letter as conventional for denoting Archiphonemes.

Like most archiphonemes, the distribution of this phoneme is very limited; within the Tokyo standard dialect it can only occur after a vowel, and before any of /t, p, k, s/. This phoneme however must still be realized in some way and make a difference in pronunciation; this is where archiphonemes become interesting, because they are typically realized by their effect on surrounding phonemes, which is why their distribution is so limited.

Now, it is often said that /Q/ is realized by geminating the following consonant. This is only arguably true in the case of /s/ where for a fricative “geminating” is a very abstract term since fricatives can be held indefinitely unlike plosives; when /Q/ is followed by /s/ it is indeed realized simply by holding /s/ for the length of an extra mora.

The sequences of /Qt, Qp, Qk/ are not realized in Japanese by geminating the following consonant; this is something that is repeated very often in lay literature and even some specialized literature but is absolutely false and I'll show why. It is realized by a mora of silence in this case; this also maps onto the perception of /Q/ by Japanese speakers who often claim to perceive it as an empty phoneme of silence for a mora. This goes back it being a consonant; it is effectively “a consonant of silence”.

Onto the audio analysis comparison:

JP vs Fin

The top two are from a Japanese rendition of “ちょっと”; the speaker Strawberrybrown collected from here; the bottom two are from the Finnish word “että” collected from the speaker Koobee here.

It is obvious that in “että”, there is a small amplitude spike before the “tä” that is lacking in “ちょっと”, but that is not all, in the spectrogram there is also a small thin dark vertical line in the same place that is indicative of a plosive sound. There is no doubt that in Finnish there truly are two plosives, in this case two [t] sounds that occur in succession as you will also find in Arabic, Latin, or any other language with true consonant gemination.

This is missing in Japanese, there is nothing, no fricative, no vowel, no plosive, there is simply a mora of relative silence before the /t/, which does show the characteristic dark, then vertical band. You can verify yourself that this is reproducible with any Japanese word that features /Qt, Qp, Qk/ — the /Q/ archiphoneme, commonly called the “moraic obstruent” if you wish to learn more about it, is not realized in Japanese by doubling plosives, this is a myth that is very common, even in some specialized literature.

Now, onto the /Qs/ combination however for completeness' sake:

enter image description here

This is SPCyan's pronunciation from here.

As you can see, there is no silence here; the pattern on the spectrogram shows that the fricative in /aQsari/ is simply stretched and forms one long pattern on a spectogram that is consistent with a fricative. Nevertheless, it is also visible that it's a less loud and dense fricative than from where the real /s/ starts and more frequencies become filled in, so that's an interesting thing.

But at the end of the day, despite <っ> being conventionally romanized as a doubled consonant it “doubles” no consonant; it's realized as a moral of silence before /k, p, t/ and it only stretches /s/ — it cannot occur in the standard dialect before any other sound but in some dialects it can occur more freely where the realization becomes even more varied.

P.S.: more I incidentally lately came across a a piece of research which investigates the perception of /Qs/ by Japanese native speakers and concludes that they have a hard time differentiating the normal realization from a true mora of silence, which provides evidence that to Japanese speakers, the underlying form is indeed a mora of silence, not a gemination.


The small つ (written as っ) is used to represent a very brief pause before the next consonant. These occur in the readings of Kanji and in hiragana grammatical conjugations. This is Romanised as a double consonant and used to represent them (with ッ) in foreign words. The reason that つ is used is that "tsu" sounds are often replaced with pauses in compound words. This is similar to the voicing of second Kanji in compound words (such as [川]{river} being read as かわ or がわ in different words).

For example, use in grammatical conjugations:


I bought the Apple


It was delicious


Please wait

Use in Kanji readings:




Sapporo (City)


Hokkaido (Island/Prefecture)

This pause is also used for sudden stops in conversational speech:





Since the sound following depends on the next Kanji, not they one preceding it, the っ could occur before any sound that occurs native in Japanese (including voiced consonants G, Z, J and yoon syllables). However, notice that Fa, Fi, Fe, C, V, and Wi do not occur natively in Japanese and are only used in foreign names (or very recent loanwords).

Note that while っ is romanised as a double consonant, it is often not pronounced this way, although the following consonant may be stressed. See this answer for more details.

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    If this answer were accurate, you would be able to pronounce っ in あっさり or マッハ or ヘッド by "pausing", but you can't. – snailplane Jun 16 '18 at 12:13
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    Many textbooks (written by Native speakers) describe it as a pause (or the silent tsu). I’ve described it specifically in native Japanese words since foreign loanwords (where the usage differs) has been excellently described already. This is also why there are only “double consonants” and no other consonant diphthongs in Japanese. – Tom Kelly Jun 16 '18 at 12:17
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    あっさり is a native Japanese word, and yet you must extend the /s/ sound rather than pause if you want to pronounce it. It is hardly an exception; "pause" is incorrect as a description for gemination. By the way, a "diphthong" is a vowel sound which changes in quality from one place of articulation to another over time. Unfortunately, your last sentence doesn't appear to mean anything in particular. – snailplane Jun 16 '18 at 12:21
  • It’s a very difficult sound to describe. I’ve seen many textbooks attempt to do so in different ways but most call it a very short pause. Of course, there’s no substitute to being in Japan or talking to native speakers to learn correct pronunciation (romanising words can only go so far). I hope that putting it in context and giving some different examples helps some people. If you think you can describe it more accurately, please be my guest. Please try to do so in non-technical terms: not all Japanese learners are linguists. – Tom Kelly Jun 16 '18 at 12:30
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    Zorf’s answer above convinces me Tom Kelly was onto something, though it took nuance to understand. – Yatharth Agarwal Sep 24 '20 at 22:33

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