Celtic languages are a branch of the Indo-European languages. They were spoken across western Europe in ancient times, but are now limited to a few enclaves in the British Isles and on the peninsula of Brittany in France.

There are four main groups of Celtic languages, of which the first two are now long extinct:

• Gaulish and its close relatives, Lepontic, Noric, and Galatian. These languages were once spoken in a wide arc from France to Turkey and from the Netherlands to northern Italy.
• Celtiberian, anciently spoken in Aragon and elsewhere in Spain.
• Goidelic, including Irish Gaelic, Scottish Gaelic, Manx, and Shelta
• Brythonic, including Welsh, Breton, Cornish, Cumbric, the hypothetical Ivernic, and possibly Pictish

The separation of these groups probably occurred well before 1000 BC, possibly with an early split of an Insular Celtic branch. The early Celts are commonly associated with the archaeological Urnfield culture.

The four groups are traditionally split into two branches, but there are two competing schemata. The first links Gaulish with Brythonic in a P-Celtic node, leaving Celtiberian and Goidelic together as Q-Celtic. The differences between P and Q languages are most easily seen in the word for son, mac in Q (hard K sound) and map in P languages. This grouping is probably paraphyletic, and the alternative schema links Goidelic and Brythonic together as an Insular Celtic branch, leaving Gaulish and Celtiberian as Continental Celtic. According to this system, the development from Q to P might have occurred independently. The proponents of the Insular Celtic hypothesis point to other shared innovations among Insular Celtic languages, including inflected prepositions and VSO word order. There is, however, no assumption that the Continental Celtic languages descend from a common "Proto-Continental Celtic" ancestor. Rather, Continental Celtic is simply a convenient term for those Celtic languages that are not Insular Celtic.

(Note: Breton is closely related to Cornish and is thus classified with Insular Celtic. Brittany is known to have been settled from Britain in historical times. Some elements of Breton may originate in the Continental Celtic languages, however these would have the status of borrowings, much like Gaulish borrowings in French.)

There are legitimate scholarly arguments in favour of both the Insular Celtic hypothesis and the P-Celtic hypothesis. Proponents of each schema dispute the accuracy and usefulness of the other's categories. It should, however, be remembered that this dispute is purely academic in that they concern the relationship between modern-day groups of languages and groups that are now extinct. No serious authority disputes that the Celtic languages spoken at present divide into Goidelic and Brythonic clusters. When referring only to the modern Celtic languages, 'Q-Celtic' and 'P-Celtic' may be taken as synonymous with Goidelic and Brythonic, respectively (although this terminology usually implies acceptance of the overall P-Celtic hypothesis).

Within the Indo-European family, the Celtic languages have sometimes been placed with the Italic languages in a common Celto-Italic (or Italo-Celtic) subfamily.

Characteristics of Celtic Languages

Although there are many differences between the individual Celtic languages, they do show many family resemblances. While none of these characteristics is necessarily unique to the Celtic languages, there are few if any other languages which possess them all. They include:

• Initial consonant mutation.
• Inflected prepositions.
• VSO word order as standard.
• Two grammatical genders.
• Definite but no indefinite article.
• Genitive construction by apposition.
• Counting by twenties.

Examples:
Ná bac le mac an bhacaigh is ní bhacfaidh mac an bhacaigh leat. (Irish example)
(Literal translation) Don't bother with son the beggar's and not will-bother son the beggar's son with-you.

• bhacaigh is the genitive of bacach. The i is the genitive inflection; the bh is a mutation.
• leat is the second person form of the preposition le.
• The order is VSO in the second half.

pedwar ar bymtheg a phedwar ugain (Welsh example)
four on fifteen and four twenties

• bymtheg is a mutated form of pymtheg, which is pump five plus deg ten. Likewise, phedwar is mutated from pedwar.
• The multiples of ten are deg, ugain, deg ar hugain, deugain, hanner cant, trigain, deg a thrigain, pedwar ugain, deg a phedwar ugain, cant.

See also

• Language families and languages
• Celt (for the ancient Celts)
• Modern Celts

References

Gray, R. and Atkinson, Q.D. 2003. Language-tree divergence times support the Anatolian theory of Indo-European origin. Nature. 426:435-439.