The 6 Celtic Languages and How They Compare

Six living Celtic languages have their traditional homes in Ireland, Wales, Scotland, Brittany, Cornwall and the Isle of Man, with speakers and learners worldwide. Cornish and Manx have active revival movements. This guide separates their family relationships from the different ways speaker numbers are measured.

This guide covers all six: how they're related, how many speakers each has, what makes them distinctive, and how they compare to each other.

Celtic Languages Family Tree

The six living Celtic languages descend from Proto-Celtic and are conventionally grouped into Goidelic and Brythonic. This simplified tree shows those modern groups, not a settled classification of every ancient Celtic language.

P-Celtic and Q-Celtic: the key sound change

The Q-Celtic and P-Celtic labels describe a historical sound correspondence: Proto-Celtic *kʷ developed into a k sound in Goidelic, usually written c in Irish, and p in Brythonic. Later sound changes can obscure that correspondence. Compare:

Shared features include initial consonant mutations and inflected prepositions. Verb-first sentences are common, but word-order patterns differ, particularly in Breton and Cornish. Answers to yes/no questions also depend on the language and question type.

Irish (Gaeilge)

Census measure: 1,873,997 people aged 3+ in Ireland reported being able to speak Irish in 2022; 71,968 reported daily use outside education.<br/>Where: Ireland, including Gaeltacht communities across several counties, Northern Ireland and diaspora communities.<br/>Status: An official language of Ireland and the European Union.

Irish is taught in schools in Ireland and has dedicated media, including TG4 and Raidió na Gaeltachta. Classroom knowledge and everyday community use are different measures. For a learning pathway, see How to Learn Irish.

Welsh (Cymraeg)

Census measure: About 538,000 usual residents of Wales aged 3+ reported being able to speak Welsh in 2021. This measures ability, not frequency of use.<br/>Where: Wales, with communities elsewhere, including Patagonia.<br/>Status: Welsh has official status in Wales. The Welsh Government aims for one million speakers by 2050.

Welsh has Welsh-medium education, daily television through S4C and a wide range of learning materials. For a practical learning pathway, see How to Learn Welsh.

Scottish Gaelic (Gàidhlig)

Census measure: Scotland’s 2022 census recorded 69,701 people able to speak Gaelic. A wider total of 130,161 had some ability to speak, read, write or understand it.<br/>Where: Scotland, particularly the Highlands and Islands, with communities elsewhere.<br/>Support: Gaelic-medium education, Bòrd na Gàidhlig and BBC ALBA.

Scottish Gaelic is closely related to Irish — they shared a common literary language until roughly the 17th century. Today, there's moderate mutual intelligibility in writing but spoken conversation between the two is difficult without prior exposure. For a detailed comparison, see Irish vs Scottish Gaelic.

Breton (Brezhoneg)

Dated survey estimate: A 2018 TMO survey estimated about 207,000 Breton speakers over 15 across the five departments of historic Brittany. This is a historical estimate, not a current total.<br/>Where: Brittany, northwest France.<br/>Support: Regional organisations, bilingual education and Diwan immersion schools.

Breton is the only one of the six whose traditional homeland is on mainland continental Europe. It belongs to the Brythonic branch alongside Welsh and Cornish, rather than descending from ancient Gaulish. Its revitalisation movement sustains Breton-medium education and media.

Cornish (Kernewek)

Census measure: The ONS analysis of Cornish identity reports about 565 Cornish main-language responses in England and Wales in 2021. This does not count everyone who can speak or is learning Cornish.<br/>Where: Cornwall and communities elsewhere.<br/>Status: Recognised under the European Charter for Regional or Minority Languages.

Modern Cornish revival draws on historical texts, teaching and community use after traditional community transmission declined. Different spelling traditions have contributed to that revival. Cornish belongs to the Brythonic branch alongside Breton and Welsh.

Manx (Gaelg)

Census reporting: Reporting on the Isle of Man’s 2021 census, Isle of Man Today recorded 2,223 people with some understanding of Manx. This is not a count of fluent speakers.<br/>Where: Isle of Man.<br/>Support: Community learning and Manx-medium education, including Bunscoill Ghaelgagh.

Manx is a Goidelic language related to Irish and Scottish Gaelic. Ned Maddrell, the last speaker from its traditional native-speaking community, died in 1974. Education and community efforts continue its revival. Its spelling differs markedly from the conventions used in Irish and Scottish Gaelic.

How They Compare

Can They Understand Each Other?

Within branches: Related vocabulary and structures can help a learner, but comprehension depends on dialect, exposure and study. Irish and Scottish Gaelic are close relatives. Welsh, Cornish and Breton share a Brythonic ancestry without being interchangeable.

Across branches: Knowing Irish does not make Welsh understandable without learning it, or vice versa. Shared grammatical features can provide useful comparisons, but vocabulary and pronunciation differ substantially.

Continental Celtic (Extinct)

The family also includes extinct languages conventionally grouped geographically as Continental Celtic: Gaulish in parts of western Europe, Celtiberian in the Iberian Peninsula, Galatian in central Anatolia and Lepontic in the Alpine region. Their histories of language shift were not identical.

At their peak, Celtic languages were spoken across most of western and central Europe. The contraction to the Atlantic fringe was driven by Roman expansion, Germanic migration, and later by English and French linguistic dominance.

Which Celtic Language Should You Learn?

The practical answer depends on your connection and goals:

• Irish if you have Irish heritage, want the largest Goidelic community, or are interested in Irish culture, literature, and media.
• Welsh if you have Welsh connections, live in or plan to visit Wales, or want the Celtic language with the strongest community infrastructure and career relevance.
• Scottish Gaelic if you have Scottish connections or want to engage with Highland culture.
• Breton if you have Breton connections or are interested in the only continental Celtic language.
• Cornish or Manx if you have a connection to those communities or want to support a revival language.

If you have no specific connection, Irish or Welsh both offer extensive learning resources, communities and media to practise with. blas. supports both. Choose the language whose people, places and culture you want to engage with.