From the wikipedia article:

"The definition of a mora varies. In 1968, American linguist James D. McCawley defined it as "something of which a long syllable consists of two and a short syllable consists of one".

It's unclear to me in my readings, whether moras have to do with applying categorical perception to durations, or whether more strongly they imply that each "count" is literally the same duration of time.

For an example of the weaker statement, it could be that the first mora takes 1 unit of time, and the second mora takes somewhere between 1/2 and 1 units of time. The additional time, so long as it's not too short or long, pushes the perception of the duration into the second category.

The stronger statement says that each mora takes the same unit of time to articulate.

  • 2
    In all moraic languages I know of, long syllables are not literally physically double as long as short ones. It is a psychological perception that abstracts away all sorts of factors that affect the physical duration of syllables, like the specific consonants and vowels they're made of (e.g. Japanese /a/ tends to be longer than /i/) , prosody etc. Nov 7, 2019 at 18:46
  • 1
    Adopting McCawley's definition, the answer to your question is clearly "yes". It follows from the meaning of "quantized" -- the mora count provides the quantization.
    – Greg Lee
    Nov 10, 2019 at 5:25
  • I believe you mean quantified. quantisized is a physics and/or electronics term
    – Lambie
    Feb 14, 2023 at 23:24

2 Answers 2


I think that you've asked a complicated question. I'll try to split my answer into several parts.

First, on the topics of "duration" and quantization. A mora is a phonological unit. As with vowel quality, "length" is an area where languages appear to construct phonological categories that are discrete even though phonetic duration is naturally gradient. (Gradiency might also exist in phonology in addition to discrete categories, but phonological gradiency is a more controversial concept that you don't need to investigate to understand the concept of a mora.) A mora does not directly equal a unit of phonetic duration (although pedagogical descriptions of how moras function in languages like Japanese often simplify the idea by describing it in terms of phonetic duration).

As melissa_boiko said in a comment, it's typical for long syllables to not be realized with twice the phonetic duration of short syllables. Given that, you might ask why McCawley specified that long syllables contain "two" moras? It's not just because two is the next integer after one. In some languages, we can find evidence that heavy syllables are in some way equivalent on the phonological level to two light syllables when we look at the structure of some kinds of poetry. For example, Japanese haiku is typically described as being based on mora count, and Classical Latin quantitative meter allows the option of either two short syllables or one long syllable in certain positions. However, such evidence does not exist in all languages, so the situation is not always clear. The occurrence of moras in English for example is more debatable.

Some languages have been analyzed as having trimoraic syllables based on the “extra-heavy” behavior of syllables ending in VːC/VVC or VCC, but I’m not sure what kind of evidence has been found indicating that superheavy syllables contain specifically three units of length. (In Classical Latin, there are syllables ending in VCC or VːC/VVC, but they behave identically in terms of prosody to syllables ending in Vː/VV or VC, so I see no basis for saying that Classical Latin syllables can be any longer than two moras.) Since you posted the question, I have started looking at some papers by Kevin M. Ryan that have some interesting discussion of the topic of phonological weight. In a 2016 preprint of the article "Phonological weight", Ryan cites Bruce Hayes 1979, "The rhythmic structure of Persian verse", for the statement that in some kinds of Persian verse, superheavy syllables are treated as metrically equivalent to heavy + light sequences. In that case, it seems like the math does indeed work out if superheavy syllables are analyzed as containing three moras (vs. a regular heavy syllable containing two moras), since 3 = 2 + 1. However, I haven't been able to get my hands on the 1970 Hayes paper yet, so I can't describe the relevant Persian data any further.

  • Are you speaking of Classical or Medieval Latin poetry? Medieval Latin was stress-timed and may have been non-moraic for all I know.
    – jlawler
    Nov 7, 2019 at 23:10
  • 2
    @jlawler: I'm referring in this answer to Classical Latin poetry with quantitative (likely Greek-influenced) meters such as the dactylic hexameter used in Vergil's Aeneid and Ovid's Metamorphoses. Latin did have other kinds of meters, both in later and earlier periods, but the quantitative meters are a well known type of poetry in the Classical period. Nov 7, 2019 at 23:27
  • I think that thinking about the actual phonetic length of the realization of two basic units is especially problematic for heavy syllables consisting of short vowels and closed by a consonant. Should one then spend one mora on the short wovel and one more on the consonant? There may well be a difference about the realization in quantitative verse and in normal speech. Especially in languages that do distinguish short and long phonemes but are still stressed and naturally prefer syllabotonic verse. Didn't even Latin started with such poetry and then copied Greek? Nov 10, 2019 at 11:04
  • I know that in the Czech quantitative verse rules (mainly in the 19. century) there are rules for the distintction of light and heavy syllables that are only inconsistently applied, they are not too natural but rather a convention and not a universal one. Nov 10, 2019 at 11:06
  • @VladimirF: The papers by Ryan that I have read say that in quantitative verse, closed syllables are treated as heavy in almost all languages, even if the vowel is short, but Ryan also notes that there are few languages where quantitative verse originated independently. The role of stress in pre-Classical Latin poetry is controversial and poorly understood, according to the Wikipedia article on "Saturnine" verse. Nov 10, 2019 at 12:23

There are multiple conflicting ideas about what a mora is or does. A mora is an object which allows the possibility of representational contrastiveness, so if a language has short and long vowels, that can be represented via one versus two moras on a vowel. That does not necessarily imply anything about production or perception, unless you subscribe to a theory where representational objects necessarily have perceptual correlates, or production correlates. McCawley's statement is as specific as most phonologists feel like getting. There are some generalizations about phonology that can be insightfully captured with the concept "mora". It is also not self-evident that "mora" is a valid concept in all languages.

Anything involving duration measurements is outside the domain of phonology. There is some research done in phonetics that addresses the question of how moraic representation relates to durational patterns, and the answer seems to be "it's language specific". I know only one language where "twice as long" is the rule for computing the duration of a bimoraic segment.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.