Mora (quoted from wikipedia)

Mora (plural moras or morae) is a unit of sound used in phonology that determines syllable weight (which in turn determines stress or timing) in some languages. Like many technical linguistics terms, the exact definition of mora varies. Perhaps the most succinct working definition was provided by the American linguist James D. McCawley in 1968: a mora is “Something of which a long syllable consists of two and a short syllable consists of one.” The term comes from the Latin word for “linger, delay”, which was also used to translate the Greek word chronos (time) in its metrical sense.
A syllable containing one mora is said to be monomoraic; one with two moras is called bimoraic.
In general, moras are formed as follows:
(1)A syllable onset (the first consonant[s] of the syllable) does not represent any mora.
(2)The syllable nucleus represents one mora in the case of a short vowel, and two moras in the case of a long vowel or diphthong. Consonants serving as syllable nuclei also represent one mora if short and two if long. (Slovak is an example of a language that has both long and short consonantal nuclei.)
(3)In some languages (for example, Japanese), the coda represents one mora, and in others (for example, Irish) it does not. In English, the codas of stressed syllables represent a mora (thus, the word cat is bimoraic), but for unstressed syllables it is not clear whether the codas do (the second syllable of the word rabbit might be monomoraic).
(4)In some languages, a syllable with a long vowel or diphthong in the nucleus and one or more consonants in the coda is said to be trimoraic (see pluti).
In general, monomoraic syllables are said to be light syllables, bimoraic syllables are said to be heavy syllables, and trimoraic syllables (in languages that have them) are said to be superheavy syllables. Most linguists believe that no language uses syllables containing four or more moras.
In India, the mora was an acknowledged phenomenon well over two millennia ago in ancient Indian linguistics schools studying the dominant scholarly and religious lingua franca of Sanskrit. The mora was first expressed in India as the mātrā. For example, the short vowel "a" (pronounced like a schwa) is assigned a value of one mātrā, the long vowel "ā" is assigned a value of two mātrās, and the complex vowel "ai" (which is composed of three simple short vowels, namely "a"+"a"+"i", or one long and one short vowel, namely "ā"+"i") is assigned a value of three mātrās. Sanskrit prosody and metrics has a deep history of taking into account moraic weight, as it were, rather than straight syllables, divided into "laghu" ("light") and "guru" ("heavy") feet based on how many moras can be isolated in each word. Thus, for example, the word "kartṛi", meaning "agent" or "doer", does not contain, contrary to intuitive English prosodic principles, simply two syllabic units, but rather contains, in order, a "guru"/"heavy" foot and a "laghu"/"light" foot. The reason is that the conjoined consonants 'rt' render the normally light 'ka' syllable heavy.
Japanese is a language famous for its moraic qualities. Most dialects, including the standard, use moras (in Japanese, onji) as the basis of the sound system rather than syllables. For example, haiku(三行俳句詩) in modern Japanese do not follow the pattern 5 syllables/7 syllables/5 syllables, as commonly believed, but rather the pattern 5 moras/7 moras/5 moras. As one example, the Japanese syllable-final n is moraic, as is the first part of a geminate consonant. For example, the word Nippon (one of the pronunciations of 日本, the name for "Japan" in Japanese) has four moras (ni-p-po-n); the four characters used in the hiragana spelling にっぽん match these four moras one to one. Thus, in Japanese, the words Tōkyō (to-o-kyo-o とうきょう), Ōsaka (o-o-sa-ka おおさか), and Nagasaki (na-ga-sa-ki ながさき) all have four moras, even though they have two, three, and four syllables, respectively.
In Luganda, a short vowel constitutes one mora while a long vowel constitutes two moras. A simple consonant has no moras, and a doubled or prenasalised consonant has one. No syllable may contain more than three moras. The tone system in Luganda is based on moras.
In Hawaiian, both syllables and moras are important. Stress falls on the penultimate(倒數第二的) mora, though in words long enough to have two stresses, only the final stress is predictable. However, although a diphthong, such as oi, consists of two moras, stress may only fall on the first, a restriction not found with other vowel sequences such as io. That is, there is a distinction between oi, a bimoraic syllable, and io, which is two syllables.