Mutual intelligibility

In linguistics, mutual intelligibility is a relationship between different but related language varieties in which speakers of the different varieties can readily understand each other without prior familiarity or special effort. Mutual intelligibility is sometimes used to distinguish languages from dialects, although sociolinguistic factors are often also used.

Czech and Slovak have a long history of interaction and share vocabulary, grammatical and orthographic features.

Intelligibility between varieties can be asymmetric; that is, speakers of one variety may be able to better understand another than vice versa. An example of this is the case between Afrikaans and Dutch. It is generally easier for Dutch speakers to understand Afrikaans than for Afrikaans speakers to understand Dutch.

In a dialect continuum, neighbouring varieties are mutually intelligible, but differences mount with distance, so that more widely separated varieties may not be mutually intelligible. Intelligibility can be partial, as is the case with Azerbaijani and Turkish, or significant, as is the case with Bulgarian and Macedonian.

Asymmetric intelligibility refers to a relationship between two partially mutually intelligible languages in which one group of speakers has greater difficulty understanding the other language than vice versa, due to various linguistic or sociocultural factors. For example, if one language is related to another but has simplified its grammar, the speakers of the original language may understand the simplified language, but not vice versa. To illustrate, Dutch speakers tend to find it easier to understand Afrikaans as a result of Afrikaans's simplified grammar.

Sign languages are not universal and usually not mutually intelligible, although there are also similarities among different sign languages. Sign languages are independent of spoken languages and follow their own linguistic development. For example, British Sign Language and American Sign Language (ASL) are quite different linguistically and mutually unintelligible. The grammar of sign languages does not usually resemble that of the spoken languages used in the same geographical area. To illustrate, in terms of syntax, ASL shares more in common with spoken Japanese than with English.

Some linguists use mutual intelligibility as the primary linguistic criterion for determining whether two speech varieties represent the same or different languages.

A primary challenge to this view is that speakers of closely related languages can often communicate effectively when they choose to. For example, in the case of transparently cognate languages recognized as distinct such as Spanish and Italian mutual intelligibility is neither binary nor absolute, but exists along a spectrum, influenced by numerous speaker-specific and contextual variables.