A term used in traditional studies of Metrics to refer to a minimal unit of metrical time equivalent to a short syllable; it has come to be used in recent phonological theories which pay attention to prosodic features.
A mora is defined by Han (1962, in Hoequist 1985) as a unit equal to a short syllable. Ladefoged (1982: 226 in Vance 1987) states that "A mora is a unit of timing. Each mora takes about the same length of time to say" (p.62). Moras are the units to which metrical structure may refer.
Long vowels are often considered to be bimoraic, while short ones are monomoraic. This would explain the difference in behaviour with respect to stress-rules between these two classes of vowels in quantity-(in)sensitivity">quantity-sensitive languages.
(From: A dictionary of Linguistics & Phonetics, LIT. Hyman. 1985)
Syllables are parsed solely into moras, which in their turn function as weight united: a syllable with one mora is light, as in (Ia), and with more than one mora, heavy, as in (Ib).
σ σ σ σ
μ μ μ μ μ
(Ic) f a t o
Hyman(1984, 1985) and McCarthy and Prince(1986) have suggested a more radical proposal. The prosodic tier they favor has just one kind of unit, as in X theory, but instead of representing a segment, this unit represents the notion of mora. The mora has a dual role in this theory. First, it represents the well-known contrast between light and heavy syllables: a light syllable has one mora, a heavy syllable two. Second, the mora counts as phonological position: just as in earlier theories, a long segment is normally represented as being doubly linked. (see figures above)
An important aspect of both Hyman(1984, 1985) and McCarthy and Prince(1986): Work is the claim that the moraic structure of languages can vary. For instance, in some languages (such as Latin) CVV and CVC syllables count as heavy and CV as light. The claim of moraic theory is that these languages differ in their rules for assigning moraic structure; CVC is assigned two moras in Latin and one mora in Lardil.
Languages that exhibit a syllable weight distinction typically also have a vowel length distinction, and vice versa. This is to be expected in a moraic theory, since the same formal configuration, bimoraic syllables, is used to represent both. The existence of language-particular moraic structure is an important part of the theory: it predicts that in the absence additional adjustment rules, the same criterion of syllable weight will be relevant throughtout the phonology of a single language(Hyman(1985:12)). Thus, in Latin(Allen1973) CVC counts as heavy for multiple rules and constraints (for instance, stress, metrics, and Iambic Shortening). In contrast, in Lardil several rules (truncation, augmentation, reduplication) count CVC as light (Hale 1973, Wilkinson 1988).
Although isolated problems exist, the idea of language-particular moraic structure seems well motivated. Contrary to the prediction of SPE (Chomsky and Halle 1986), a typical phonology is not a random collection of posssible rules but an integrated system. By factoring out moraic structure as an overall property of a labguage’s phonology, we come closer to a theory that describes phonological systems rather than just rule collections.
(Source: Bruce Hayes. Compensatory Lengthening in Moraic Phonology. 1989.)
IV. What is Moraic Languages
Rod Johnson wrote: Moraic languages are those in which the mora plays a part in the phonology or the metrical system.
Kenneth Pike's Phonemics: The distinction between mora-timing and syllable-timing languages. There were a number of phonetic studies in the 1950s and 1960 attempting to either establish or deny the vailidty of the distinction, but it seems no definitive consensus was ever reached.
Rod Johnson wrote: Let me just point out, as a matter of terminology, that "mora-timing" does not mean "moraic". In a mora-timing language, each mora takes approximately the same time to pronounce--thus a heavy (2-mora) syllable will take twice as long as a light one. This phenomenon is also called "isochrony, and is mainly a phonetic one. "Moraic" is a phonological phenomenon, in which a language is sensitive to the heavy/light distinction, regardless of timing (especially in stress or accent). So a language could be moraic but not mora-timing. The two ideas are quite different.
Steven Schaufele wrote:
Sanskrit is a mora-counting language in the same way that Latin and Classical Greek are. Short vowels count as 1 mora, long vowels as 2, and any consonant in the coda (not only nasals) counts as 1 mora.
ya.jna.m "sacrifice" (acc.)
vi.kra.a.n.ti.m "victorious stride"
The critical distinction is between 1-mora syllables and syllables of more than one mora; all traditional Sanskrit poetic prosody depends upon this distinction between `light' and `heavy' syllables. Little attention is paid to the distinction between 2-mora and 3-mora syllables.
Moraic features are similar to Sanskrit above.
3. CLASSICAL GREEK
lova lo.o.va HLL "bed"
diena di.e.na LLH "afternoon"
rytas ri.i.ta.s HLLL "morning"
ac^iu a.a.Cu.u HLLL "thank you"
labas la.a.ba.s LHLL "good"
lovys lo.o.vi.i.s LLLHL "tub"
vakaras va.a.ka.ra.s LHLLLLL "evening"
3. JAPANESE (Standard Japanese)
SEN-EN se.N.e.N [see~ee~n] HLLL one thousand yen
SENNEN se.N.ne.N [see~nee~n] HLLL one thousand years
SEIEN se.e.e.N [se::e~n] LHHH cheering
SEINEN se.e.ne.N [se:nee~n] LHHH adolescent
SEQKEN se.Q.ke.N [se_kee~n] LHHH soap ([_] shows silence)
TEQSEN te.Q.se.N [tes:ee~n] LHHH iron wire
UMA u.ma [u-ma] LH horse (ordinary)
POKEQTO po.ke.Q.to [poke_to] LHLL pocket
4. KILIVILA (KIRIWINA)
ba.la "I will go"
e.la "he/she goes"
ba.ki.u.m "I will do secretly"
bi.ka.tu.po.i.a.i.m.si "they will ask you"
m.m.mo.ta "this (bundle)"
la.o.di.la "bush, jungle"
i.si.si.a.si "they stay (in a place)"
i.ka.tu.po.i.a.i.da.si "he asks us"
(Source: Kawagashkira Nobuyuki Linguist List 7.943 Fri Jun 28 1996)