An isolating language is a type of language with a morpheme per word ratio close to one, and with no inflectional morphology whatsoever. In the extreme case, each word contains a single morpheme. Examples of widely spoken isolating languages are Yoruba^[1] in West Africa and Vietnamese^[2][3] (especially its colloquial register) in Southeast Asia.

A closely related concept is that of an analytic language, which uses unbound morphemes or syntactical constructions to indicate grammatical relationships. Isolating and analytic languages tend to overlap in linguistic scholarship.^[2]

Isolating languages contrast with synthetic languages, also called inflectional languages, where words often consist of multiple morphemes.^[4] That linguistic classification is subdivided into the classifications fusional, agglutinative, and polysynthetic, which are based on how the morphemes are combined.^[5]

Explanation

Although historically, languages were divided into three basic types (isolating, inflectional, agglutinative), the traditional morphological types can be categorized by two distinct parameters:

• morpheme per word ratio (how many morphemes there are per word)
• degree of fusion between morphemes (how separable the inflectional morphemes of words are according to units of meaning represented)

A language is said to be more isolating than another if it has a lower morpheme per word ratio.

To illustrate the relationship between words and morphemes, the English term "rice" is a single word, consisting of only one morpheme (rice). This word has a 1:1 morpheme per word ratio. In contrast, "handshakes" is a single word consisting of three morphemes (hand, shake, -s). This word has a 3:1 morpheme per word ratio. On average, words in English have a morpheme per word ratio substantially greater than one.

It is perfectly possible for a language to have one inflectional morpheme yet more than one unit of meaning. For example, the Russian word vídyat/видят "they see" has a morpheme per word ratio of 2:1 since it has two morphemes. The root vid-/вид- conveys the imperfective aspect meaning, and the inflectional morpheme -yat/-ят inflects for four units of meaning (third-person subject, plural subject, present/future tense, indicative mood). Effectively, it has four units of meaning in one inseparable morpheme: -yat/-ят.

Languages with a higher tendency toward isolation generally exhibit a morpheme-per-word ratio close to 1:1. In an ideal isolating language, visible morphology would be entirely absent, as words would lack any internal structure in terms of smaller, meaningful units called morphemes. Such a language would not use bound morphemes like affixes.

The morpheme-to-word ratio operates on a spectrum, ranging from lower ratios that skew toward the isolating end to higher ratios on the synthetic end of the scale. A larger overall ratio suggests that a language leans more toward being synthetic rather than isolating. ^[6][7]

Examples

Some isolating languages include:

• Classical Chinese^[8]
• Vietnamese^[2][3]
• Yoruba^[1]
• Khmer language
• Thai language
• Central Flores languages