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Mora

Definition:

A mora (plural: morae or moras) is a phonological timing unit smaller than or equal to a syllable. In mora-timed languages, rhythm is organized so that each mora takes approximately equal time to produce. In simple syllables (CV — consonant + vowel, like the syllable ka), one syllable = one mora. In heavier syllables containing a long vowel, a final consonant, or a vowel cluster, a single syllable may contain two morae — and takes proportionally longer to produce. Understanding morae is essential for learning Japanese, where the entire phonological and rhythmic system is mora-based. See Japanese Mora for a full treatment of morae in Japanese specifically.

Also known as: moraic unit, timing unit

In-Depth Explanation

Mora-timed vs. syllable-timed vs. stress-timed languages: Languages are traditionally grouped by their rhythmic basis. Stress-timed languages (English, German, Russian) organize rhythm around stressed syllables — unstressed syllables compress. Syllable-timed languages (French, Spanish, Mandarin Chinese) assign roughly equal duration to each syllable. Mora-timed languages (Japanese, Classical Arabic, Ancient Greek) assign roughly equal duration to each mora — making long vowels and special syllables genuinely longer-sounding, not just a perceptual effect.

Moraic structure in syllables: In phonological theory (especially Optimality Theory and metrical phonology), morae are represented as structural nodes beneath the syllable. A short vowel contributes one mora to its syllable (light syllable); a long vowel, or a coda consonant, contributes an additional mora (heavy syllable). This distinction governs:

  • Stress assignment in languages like Latin and Classical Arabic (heavy syllables attract stress)
  • Compensatory lengthening — when a consonant is deleted, its mora persists and lengthens the preceding vowel
  • Poetic meter in classical languages (Greek and Latin meter is based on heavy vs. light syllables, i.e., moraic weight)

Morae in Japanese: Japanese is the language most commonly encountered by language learners in which morae are directly observable and pedagogically important. In Japanese, the following are each one mora:

  • Any CV syllable (か、き、く、け、こ, etc.)
  • Any V syllable (あ、い、う、え、お)
  • The special mora nasal ん (N)
  • The special sokuon っ (geminate consonant onset)
  • The second mora of a long vowel (e.g., おう、ああ、おお)

Failing to give ん and っ their full moraic weight is one of the most audible markers of a non-native Japanese accent. The word ちょっと (chotto, “a little”) has three morae: ちょ + っ + と, and must be spoken with all three timed beats. See Japanese Mora and Pitch Accent for further detail.

Morae and pitch accent: Japanese pitch accent is assigned at the moraic level, not the syllable level. A word’s accent pattern specifies which mora carries the high-to-low pitch drop; because some syllables contain two morae (e.g., long vowels), the accent position can fall within what would be a single syllable in syllable-counting terms.

Common Misconceptions

  • Morae are not syllables. A syllable may contain one or two morae. The syllable man in Japanese (まん) contains two morae (ま + ん) even though it is one syllable in the intuitive sense.
  • Mora-timing is a tendency, not a precise clock. The moraic isochrony principle (each mora = equal time) is an idealization; actual speech shows variation — but the perceptual and phonological organizing role of morae is real.
  • Only some languages use morae centrally. English has moraic structure in the phonological analysis but is not mora-timed in its rhythm — English speakers rarely need to think in morae explicitly.

Last updated: 2026-04

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