Sokuon

The sokuon (促音) is a Japanese symbol in the form of a small hiragana or katakana tsu. In less formal language, it is called chiisai tsu (小さいつ) or chiisana tsu (小さなつ), meaning "small tsu". It serves multiple purposes in Japanese writing.

Appearance
In both hiragana and katakana, the sokuon appears as a tsu reduced in size:

Use in Japanese
The main use of the sokuon is to mark a geminate consonant, which is represented in most romanization systems by the doubling of the consonant, except that Hepburn romanization writes a geminate ch as tch. It denotes the gemination of the initial consonant of the symbol that follows it.

Examples: • Pocky, a Japanese snack food, is written in kana as ポッキー, which is

In rōmaji, this is written pokkī, with the sokuon represented by the doubled k consonant.

•, the te form of the verb, is composed of:

In the rōmaji rendering, matte, the sokuon is represented by the doubling of the t consonant.

•, meaning "here", is composed of:

In Hepburn romanization, kotchi, the sokuon is represented by the t consonant, even though the following consonant is ch. This is because rōmaji ch actually represents (voiceless alveolo-palatal affricate), and the sokuon before it doubles the sound. The Kunrei-shiki and Nihon-shiki romanization systems write this syllable as ti (and its geminate version as tti) so the exception does not arise.

The sokuon never appears at the beginning of a word or before a vowel (a, i, u, e, or o), and rarely appears before a syllable that begins with the consonants n, m, r, w, or y. (In words and loanwords that require geminating these consonants,, , , , and are usually used, respectively, instead of the sokuon.) In addition, it does not appear before voiced consonants (g, z, d, or b), or before h, except in loanwords, or distorted speech, or dialects. However, uncommon exceptions exist for stylistic reasons: For example, the Japanese name of the Pokémon species Cramorant is ウッウ, pronounced.

The sokuon is also used at the end of a sentence, to indicate a glottal stop (IPA, a sharp or cut-off articulation), which may indicate angry or surprised speech. This pronunciation is also used for exceptions mentioned before (e.g., a sokuon before a vowel kana). There is no standard way of romanizing the sokuon that is at the end of a sentence. In English writing, this is often rendered as an em dash. Other conventions are to render it as t or as an apostrophe.

In the International Phonetic Alphabet, the sokuon is transcribed with either a colon-like length mark or a doubled consonant:
 * "come" (来て) –
 * "postage stamp" (切手) – or
 * "clams" (あさり) –
 * "easily" (あっさり) – or

The sokuon represents a mora, thus for example the word Japan consists of only two syllables, but four morae: ni-p-po-n.

Use in other languages
In addition to Japanese, sokuon is used in Okinawan katakana orthographies. Ainu katakana uses a small ッ both for a final t-sound and to represent a sokuon (there is no ambiguity however, as gemination is allophonic with syllable-final t).

Computer input
There are several methods of entering the sokuon using a computer or word-processor, such as,  ,  , etc. Some systems, such as Kotoeri for macOS and the Microsoft IME, generate a sokuon if an applicable consonant letter is typed twice; for example   generates った.

Other representations
Braille:


 * Computer encodings