Isochrony

Isochrony is a linguistic analysis or hypothesis assuming that any spoken language's utterances are divisible into equal rhythmic portions of some kind. Under this assumption, languages are proposed to broadly fall into one of two categories based on rhythm or timing: syllable-timed or stress-timed languages (or, in some analyses, a third category: mora-timed languages). In syllable-timing, there are pauses of roughly equal length between every syllable, while in stress-timing, there are pauses of roughly equal length only between every stressed syllable.

While isochrony may be a useful theoretical framework in some contexts, studies suggest that, at best, syllable structure in natural speech has only a somewhat regular rhythm and perfectly regular speech may in fact be less intelligible. Careful linguistic analysis instead reveals that isochrony may be a subjective feature of language: more a listener perception than an inherent part of a language, making it a difficult hypothesis to test. Empirical studies have been mixed: unable to directly or fully support the hypothesis but sometimes lending support to it as a general or average tendency of languages; therefore, the concept remains controversial in linguistics. According to British phonetician Peter Roach:

there is no language which is totally syllable-timed or totally stress-timed - all languages display both sorts of timing; languages will, however, differ in which type of timing predominates. Secondly, different types of timing will be exhibited by the same speaker on different occasions and in different contexts.