How many syllables are there in a Haiku?

Some of us learnt in school English lessons about a Japanese verse form called the haiku. We learnt then that a haiku contains a fixed number of syllables (17), divided into 3 lines: 5, then 7, then 5. Our English teachers encouraged us to experiment using that form in writing short, pithy verses in English.

Well, our English teachers’ explanation was slightly simplified. A Haiku contains a fixed number of moras, not a fixed number of syllables. (The term mora comes from Latin and so some writers spell its plural as morae.)

Our teacher’s simplification was reasonable: the mora is important in the sound system of Japanese and is embodied in that language’s writing system. In contrast, in English the mora plays a less prominent role than the syllable does. Moreover, the English speaking public (including children) know something about the syllable but nothing at all about the mora. So simplifying the message seems reasonable.

What is a mora?

A simple way of thinking about a mora is as a timing unit. Syllables typically contain one or two moras. A syllable with two moras takes about twice as long to say as a syllable with one mora.

Tsujimura (1996) identifies three types of mora in Japanase:

  1. A vowel, which may or may not have a consonant in front of it.
    (the second half of a long vowel forms a separate mora)
  2. The first half of a long (doubled or ‘geminate’) consonant.
  3. A syllable-final /n/

Examples of moras

The word aki (autumn) contains 2 moras:
(full stops here show boundaries between moras)
Both moras in this example are instances of the first type of mora.

An instance of the second type of mora is in gakkoo (school): ga.k.ko.o
The first half of the long consonant /kk/ is a separate mora. The first, third and fourth moras are all instances of the first type of mora.
Also, the two halves of the long vowel /oo/ fall into two separate moras.

The word mikan (orange) contains 3 moras: mi.ka.n
The first two moras are instances of the first type of mora. The third mora is an instance of the third type: syllable-final /n/
The second and third moras together form a single syllable: /kan/

Examples from Tsujimura (1996)

Role of moras in Japanese

Moras play a more prominent role in the Japanese sound system than they do in English. For instance:

  • native Japanese speakers perceive words as made up of moras rather than syllables. For example, they perceive the word Tokyo (which contains two instances of double /oo/) as made up of 4 units corresponding to the moras (To.o.kyo.o), rather than two units corresponding to the syllables (Too-kyoo).
  • In spoken Japanese, the duration of each mora is about the same. Thus, a four-mora word lasts about twice as long as a two-mora word. Moreover, in traditional Japanese songs, every mora is assigned to one note and vice versa.
  • Moras largely determine where the stress is placed, both within simple words and within compound words. They also play a role in determining word formation.
  • Slips of the tongue and other speech errors in Japanese occur within moras, not between them, for example:
    • a /n/ that is a separate mora can replace half of a long consonant or long vowel
    • the second half of a long vowel can convert into a different vowel
  • When adults stutter in Japanese, they typically repeat the first mora of a word: do do do do domori. In contrast, in English adult stutters typically repeat single consonants: s s s s s stuttering.
  • Some people play language games that change the sound shape of a word. In Japanese, these work in a way consistent with the word’s moraic structure. For instance, Tsujimura (1996) describes a game that inserts before every mora a new mora consisting of /b/ followed by the vowel from the original mora (or consisting of /bu/ if the original mora is /n/). For example:
    • sushi becomes /
    • imooto (younger sister) becomes /
    • sinbun (newspaper) becomes /

Moras and Japanese writing

Japanese has a complex writing system, comprising:

  • Chinese-style characters known as kanji. Many of these were originally borrowed from Chinese and many others were developed in Japan. Each Kanji corresponds to a stem—to a whole word, to a component of a compound word or to the stem of an inflected word. (Typically, a Kanji corresponds to several different unrelated stems, not just to a single stem)
  • two syllabaries known collectively as Kana, and individually as Hiragana and Katakana. Hiragana is used mainly: to add inflectional endings; to write grammatical particles; or to transliterate native words for which no suitable kanji exists. Katakana is used mainly to transliterate foreign words or to provide emphasis. 

Although hiragana and katakana are known as syllabaries, they are in fact based on moras, not on syllables: one character corresponds to one mora.

Presumably kana arose as a mora-based writing system to fit well with the sound system of Japanese. But it may also be that that mora-based writing reinforces the prominence of moras in Japanese speakers’ minds, and so strengthens some of the effects discussed above.

Some consequences of mora structure

Because of the limitations on permitted forms of mora in Japanese:

  • A mora cannot contain a vowel followed by a consonant. Thus:
    • a syllable can end in a consonant, but only in one that forms a separate mora: (a) /n/; or (b) the first half of a long consonant (as in the gakkoo example above)
    • there is only consonant that a word can end in: /n/.
  • Additional vowels are inserted to break up consonant clusters in words borrowed from other languages. For example: (strike).

Syllables in Japanese

Japanese has often been called a mora-language. But although the mora plays an important role in Japanese phonology, syllables also play a role. For instance, Kubozono (1999) concludes that some phonological rules can be written only in a way that refers to both moras and syllables. For example:

  • in words borrowed from other languages, the word stress goes on the syllable containing the antepenultimate mora.
  • whether two-mora words are stressed depends partly on whether they have one syllable or two syllables.

Japanese dialects

The material in this article refers to modern standard Japanese as spoken in Tokyo. Some Japanese dialects are based on syllables, rather than moras. This was also the case for Old Japanese.

Syllables and Moras in English

English has often been called a syllable-language because syllables play a greater role than they do in a mora-based language like Japanese. Nevertheless, moras can explain some things in English. For example, how English treats a syllable depends in some cases on whether the syllable is light (containing a short vowel and ending in no consonant) or heavy (either: containing a long vowel or a diphthong; or ending in a consonant). Some theories analyse light syllables as comprising one mora and heavy syllables as containing two moras.


The question in the title of this article wasn’t the right question. A haiku does not have a fixed number of syllables; it has a fixed number of moras—17, in the pattern 5-7-5.


An Introduction to Japanese Linguistics, by Natsuko Tsujimura (1996)

Mora and Syllable, by Haruo Kubozono (1999) in The Handbook of Japanese Linguistics, edited by Natsuko Tsujimura

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