In linguistics, mutual intelligibility is recognized as a relationship between languages in which speakers of different but related languages can readily understand each other without intentional study or extraordinary effort. It is sometimes used as one criterion for distinguishing languages from dialects, though sociolinguistic factors are also important.

Intelligibility between languages can be asymmetric, with speakers of one understanding more of the other than speakers of the other understand of the first. It is when it is relatively symmetric that 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.

Intelligibility

For individuals to achieve moderate proficiency or understanding in a language (called L2) other than their mother tongue or first language (L1) typically requires considerable time and effort through study and/or practical application. However, for those many groups of languages displaying mutual intelligibility, namely, those, usually genetically related languages, similar to each other in grammar, vocabulary, pronunciation, or other features, speakers of one language usually find it relatively easy to achieve some degree of understanding in the related language(s). Languages mutually intelligible but not genetically related may be creoles and parent languages, or geographically adjacent variants of two unrelated languages.

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 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.

Mutually intelligible languages or variants of one language?

According to some definitions, two or more languages that demonstrate a sufficiently high degree of mutual intelligibility should properly not be considered two distinct languages but, in fact, multiple varieties of the same language . Conversely, it is sometimes the case that different varieties of what is considered the same language—according to popular belief, governmental stance, or historical convention—are not, in fact, mutually intelligible in practice. For example, while although Sardinian, Lombard, Liguorian, Venetian, and Sicilian may be considered "dialects" of Italian, it would be difficult, and in some cases very difficult, for monolingual speakers of these languages to communicate with each other. (For more on this, see Dialect, Dialect continuum and Pluricentric language—as well as Diasystem and Diglossia for two closely related but distinct language forms.)

List of mutually intelligible languages

Written and spoken forms

• Dutch, Afrikaans, Dutch-Flemish, Frisian and Low Saxon.

• Aromanian and Megleno-Romanian

• Bahasa Malaysia and Bahasa Indonesia

• Belarussian, Russian, and Ukrainian

• Bulgarian and Macedonian

• Catalan and Occitan

• Cornish, Breton, and Welsh (not always mutually intelligible with one another)

• Croatian, Bosnian and Serbian (when written in Latin script)

• Danish, Norwegian, and Swedish

• English and Lowland Scots

• Finnish and Estonian

• French and Walloon

• Friulian, Ladin and Romansch

• Galician and Portuguese

• Galician and Spanish

• Italian and Friulian

• Italian and Sicilian (Sicilian is not officially recognized as a separate language from Italian)

• Italian and Spanish (very similar pronunciation, easily understanding, only need a little time of interaction to get used to the other language in both ways)

• Punjabi, Seraiki, and Hindko

• Romanian and Moldovan, which are actually the same language differentiated due to political reasons.

• Romanian and Aromanian (not always mutually intelligible)

• Samoan and Tongan

• Spanish and Portuguese (easily understanding; only need a few weeks of interaction to get used to the other language in both ways)

• Spanish, Haketia and Ladino (both Hatekia and Ladino are based on Fifteenth-Century Spanish, with influence from Hebrew, Arabic and French for Haketia, and Hebrew, Turkish, Greek, Italian and French for Ladino, but especially in their written form, the three languages have a high mutual degree of intelligibility; only need a few weeks of interaction is needed to get used to the other language in both ways)

• Spanish and Catalan (easily understanding; only need a few weeks of interaction to get used to the other language in both ways)

• Gaelic and Irish

• Slovak and Czech

• Slovene and Kajkavian Croatian

• Thai and Laotian

• Turkish and Azeri

• Zulu and Xhosa

Spoken forms only

• Spoken Hindi and spoken Urdu - see Hindustani language

• Spoken Uzbek and Uyghur

Written forms only

• Serbian, Croatian, Bosnian and Slovene

• Written Mandarin and written Cantonese (but not if the vernacular is written)

• Icelanders can read Old Norse with little difficulty

List of mutually intelligible languages in ancient times

• Biblical Hebrew, Moabite, and Phoenician

• Old English and Old Saxon

• Gothic, Burgundian, and Vandalic

Examples

• Varieties of Arabic

• Varieties of Chinese

• Varieties of English

• Varieties of Japanese

• Differences between Afrikaans and Dutch

• Differences between Hindi and Urdu

• Differences between Malay and Indonesian

• Differences between Norwegian Bokmål and Standard Danish

• Differences between Scottish Gaelic and Irish

• Differences in standard Serbian, Croatian and Bosnian

• Differences between Slovak and Czech languages

• Differences between Spanish and Portuguese

EU-Projects

See also

• Dialect continuum

• Dialect levelling

• Diasystem

• Lexical similarity

• Multilingualism

• Non-convergent discourse