Mutual intelligibility

In linguistics, mutual intelligibility is a relationship between languages or dialects in which speakers of different but related varieties can readily understand each other without prior familiarity or special effort. It is generally used as the most important criterion for distinguishing languages from dialects, although sociolinguistic factors are often also used.

Intelligibility between languages can be asymmetric, with speakers of one understanding more of the other than speakers of the other understanding the first. When it is relatively symmetric, it is characterized as "mutual". It exists in differing degrees among many related or geographically proximate languages of the world, often in the context of a dialect continuum.

For individuals to achieve moderate proficiency or understanding in a language (called L2) other than their first language (L1) typically requires considerable time and effort through study and/or practical application. However, many groups of languages are partly mutually intelligible, i.e. most speakers of one language find it relatively easy to achieve some degree of understanding in the related language(s). Often the languages are genetically related, and they are likely to be similar to each other in grammar, vocabulary, pronunciation, or other features.

Intelligibility among languages can vary between individuals or groups within a language population according to their knowledge of various registers and vocabulary in their own language, their exposure to additional related languages, their interest in or familiarity with other cultures, the domain of discussion, psycho-cognitive traits, the mode of language used (written vs. oral), and other factors.

There is no formal distinction between two distinct languages and two varieties of a single language, but linguists generally use mutual intelligibility as one of the primary factors in deciding between the two cases.

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