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.
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. (See Afrikaans § Mutual intelligibility with Dutch).
In a dialect continuum, neighboring 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. However, sign languages, such as American and British Sign Language, usually do not exhibit mutual intelligibility with each other.