Isochrony is the postulated
rhythm Rhythm (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million a ...
ic division of time into equal portions by a
language A language is a structured system of communication used by humans, including speech (spoken language), gestures (Signed language, sign language) and writing. Most languages have a writing system composed of glyphs to inscribe the original soun ...

. Rhythm is an aspect of
prosody Prosody may refer to: * Sanskrit prosody, Prosody (Sanskrit), the study of poetic meters and verse in Sanskrit and one of the six Vedangas, or limbs of Vedic studies * Prosody (Greek), the theory and practice of Greek versification * Prosody (Lati ...
, others being intonation, stress, and
tempo of speechSpeech tempo is a measure of the number of speech units of a given type produced within a given amount of time. Speech tempo is believed to vary within the speech of one person according to contextual and emotional factors, between speakers and also ...
. Three alternative ways in which a language can divide time are postulated: # The duration of every syllable is equal (syllable-timed); # The duration of every
mora Mora may refer to: Places * Doctor Mora, city in the Mexican state of Guanajuato * Mora (Cordillera), Bolivia * Mora, Cameroon, a town * Mora (canton), Costa Rica * Mora, Cyprus, a village * Mora, Maharashtra, India, a port near Mumbai * Mora, Port ...
is equal (mora-timed). # The interval between two stressed
syllable A syllable is a unit of organization for a sequence of speech sounds. It is typically made up of a syllable nucleus (most often a vowel A vowel is a Syllable, syllabic speech sound pronounced without any stricture in the vocal tract. Vowels a ...

s is equal (stress-timed). The idea was first expressed thus by
Kenneth L. Pike Kenneth Lee Pike (June 9, 1912 – December 31, 2000) was an American linguist Linguistics is the scientific study of language A language is a structured system of communication used by humans, including speech (spoken language), ...

Kenneth L. Pike
in 1945, though the concept of language naturally occurring in chronologically and rhythmically equal measures is found at least as early as 1775 (in ''
Prosodia Rationalis''Prosodia Rationalis'' is the short title of the 1779 expanded second edition of Joshua Steele's ''An Essay Towards Establishing the Melody and Measure of Speech, to be Expressed and Perpetuated by Peculiar Symbols'', originally published in 1775. I ...
''). This has implications for
linguistic typology Linguistic typology (or language typology) is a field of linguistics Linguistics is the science, scientific study of language. It encompasses the analysis of every aspect of language, as well as the methods for studying and modeling the ...
: D. Abercrombie claimed "As far as is known, every language in the world is spoken with one kind of rhythm or with the other ... French, Telugu and Yoruba ... are syllable-timed languages, ... English, Russian and Arabic ... are stress-timed languages." While many linguists find the idea of different rhythm types appealing, empirical studies have not been able to find acoustic correlates of the postulated types, calling into question the validity of these types. However, when viewed as a matter of degree, relative differences in the variability of syllable duration across languages have been found.

Syllable timing

In a syllable-timed language, every syllable is perceived as taking up roughly the same amount of time, though the absolute length of time depends on the
prosody Prosody may refer to: * Sanskrit prosody, Prosody (Sanskrit), the study of poetic meters and verse in Sanskrit and one of the six Vedangas, or limbs of Vedic studies * Prosody (Greek), the theory and practice of Greek versification * Prosody (Lati ...
. Syllable-timed languages tend to give syllables approximately equal prominence and generally lack
reduced vowels In phonetics, vowel reduction is any of various changes in the acoustic ''quality'' of vowels as a result of changes in stress (linguistics), stress, sonority hierarchy, sonority, vowel length, duration, loudness, articulation, or position in the ...
. French language, French, Italian language, Italian, Spanish language, Spanish, Icelandic language, Icelandic, Cantonese, Mandarin Chinese, Georgian language, Georgian, Romanian language, Romanian, Armenian language, Armenian, Turkish language, Turkish and Korean language, Korean are commonly quoted as examples of syllable-timed languages. This type of rhythm was originally metaphorically referred to as "machine-gun rhythm" because each underlying rhythmical unit is of the same duration, similar to the transient bullet noise of a machine-gun. Since the 1950s, speech scientists have tried to show the existence of equal syllable durations in the acoustic speech signal without success. More recent research claims that the duration of consonantal and vocalic intervals is responsible for syllable-timed perception.

Mora timing

Some languages such as Japanese language, Japanese, Gilbertese language, Gilbertese, Slovak language, Slovak or Luganda, Ganda also have regular pacing but are
mora Mora may refer to: Places * Doctor Mora, city in the Mexican state of Guanajuato * Mora (Cordillera), Bolivia * Mora, Cameroon, a town * Mora (canton), Costa Rica * Mora, Cyprus, a village * Mora, Maharashtra, India, a port near Mumbai * Mora, Port ...
-timed rather than syllable-timed. In Japanese, a Syllable_weight, V or CV syllable takes up one timing unit. Japanese does not have vowel length or diphthongs but ''double'' vowels, so CVV takes twice the time as CV. A final /N/ also takes as much time as a CV syllable and, at least in poetry, so does the extra length of a geminate, geminate consonant. However, colloquial language is less settled than poetic language, and the rhythm may vary from one region to another or with time. Ancient Greek and Vedic Sanskrit were also strictly mora-timed.

Stress timing

In a ''stress-timed language'', syllables may last different amounts of time, but there is perceived to be a fairly constant amount of time (on average) between consecutive stressed syllables. Consequently, unstressed syllables between stressed syllables tend to be compressed to fit into the time interval: if two stressed syllables are separated by a single unstressed syllable, as in ''delicious tea'', the unstressed syllable will be relatively long, while if a larger number of unstressed syllables intervenes, as in ''tolerable tea'', the unstressed syllables will be shorter. Stress-timing is sometimes called ''Morse-code rhythm'', but any resemblance between the two is only superficial. Stress-timing is strongly related to vowel reduction processes. English language, English, Thai language, Thai, German language, German, Russian language, Russian, Danish language, Danish, Swedish language, Swedish, Norwegian language, Norwegian, Faroese language, Faroese, Dutch language, Dutch, European Portuguese, and Persian language, Persian are typical stress-timed languages. Some stress-timed languages retain unreduced vowels. Arabic language, Arabic is sometimes cited as an example of this; however, all modern Arabic dialects are characterised by strong reduction of unstressed vowels.

Degrees of durational variability

Despite the relative simplicity of the classifications above, in the real world languages do not fit quite so easily into such precise categories. Languages exhibit degrees of durational variability both in relation to other languages and to other standards of the same language. There can be varying degrees of stress-timing within the various standards of a language. Some southern dialects of Italian language, Italian, a syllable-timed language, are effectively stress-timed. English, a stress-timed language, has become so widespread over the globe that some standards tend to be more syllable-timed than the British English, British or North American English, North American standards, an effect which comes from the influence of other languages spoken in the relevant region. Indian English, for example, tends toward syllable-timing. This does not necessarily mean the language standard itself is to be classified as syllable-timed, of course, but rather that this feature is more pronounced. A subtle example is that to a native English speaker, for example, some accents from Wales may sound more syllable-timed. A better-documented case of these varying degrees of stress-timing in a language comes from Portuguese. European Portuguese is more stress-timed than the Brazilian Portuguese, Brazilian standard. The latter has mixed characteristics and varies according to speech rate, sex and dialect. At fast speech rates, Brazilian Portuguese is more stress-timed, while in slow speech rates, it can be more syllable-timed. The accents of rural, southern Rio Grande do Sul and the Northeast Region, Brazil, Northeast (especially Bahia) are considered to sound more syllable-timed than the others, while the southeastern dialects such as the ''mineiro'', in central Minas Gerais, the ''paulistano'', of the northern coast and eastern regions of São Paulo (state), São Paulo, and the ''fluminense'', along Rio de Janeiro (state), Rio de Janeiro, Espírito Santo and Zona da Mata (Minas Gerais), eastern Minas Gerais as well the Federal District (Brazil), Federal District, are most frequently essentially stress-timed. Also, male speakers of Brazilian Portuguese speak faster than female speakers and speak in a more stress-timed manner. Peter Ladefoged, Ladefoged has proposed (citing work by Grabe and Low ) that, since languages differ from each other in terms of the amount of difference between the durations of vowels in adjacent syllables, it is possible to calculate a Pairwise Variability Index (PVI) from measured vowel durations to quantify the differences. The data show that, for example, Dutch (traditionally classed as a stress-timed language) exhibits a higher PVI than Spanish (traditionally a syllable-timed language).

The stress-timing–syllable-timing distinction as a continuum

Given the lack of solid evidence for a clear-cut categorical distinction between the two rhythmical types, it seems reasonable to suggest instead that ''all'' languages (and all their accents) display ''both'' types of rhythm to a greater or lesser extent. T. F. Mitchell claimed that there is no language which is totally syllable-timed or totally stress-timed; rather, all languages display both sorts of timing. Languages will, however, differ in which type of timing predominates. This view was developed by Dauer in such a way that a metric was provided allowing researchers to place any language on a scale from maximally stress-timed to maximally syllable-timed. Examples of this approach in use are Dimitrova's study of Bulgarian and Olivo's study of the rhythm of Ashanti Twi. According to Dafydd Gibbon and Briony Williams (linguist), Briony Williams, Welsh is neither syllable-timed nor stress-timed, as syllable length varies less than in stress-timed languages.Gibbon, D. & Williams, B. (2007)
"Timing Patterns in Welsh"
In ''Proceedings of the International Congress of Phonetic Sciences (ICPhS) XVI''.

See also

* Stress and vowel reduction in English


External links

* Roach, Peter (1998)
''Language Myths'', “Some Languages are Spoken More Quickly Than Others”
eds. L. Bauer and P. Trudgill, Penguin, 1998, pp. 150–8
Étude sur la discrimination des langues par la prosodie (pdf document)
(French language, French)
Languages’ rhythm and language acquisition (pdf document)

{{Suprasegmentals Phonetics Rhythm and meter