The six Celtic languages currently spoken are divided into two branches:
Goidelic or Gaelic, and Brythonic or British. The former branch consists of
Irish, Manx and Scottish Gaelic, while the latter branch includes Welsh,
Cornish and Breton. While there are many similarities between the languages
in each branch, there are fewer similiarities between the two branches as
they have had thousands of years to grow apart.
Differences in spelling and sound changes can disguise related words, but
there are quite a few cognates that appear in most or all of the Celtic languages.
In some cases the words in one language might be archaic or only used in place names,
and more cognates can be found in earlier versions of the the languages. Some words
are cognate within each branch of the Celtic languages, but not between the branches.
Some words beginning with p or b in the Brythonic or P-Celtic languages begin with
c, k or qu (/k/) in the Goidelic or Q-Celtic languages. For example, head is pen
in Welsh and ceann in Irish.
Some words beginning with gw in the Brythonic languages begin with f in the
Goidelic languages. For example, hair is gwallt in Welsh and falt
in Scottish Gaelic.
Some words beginning with s(e/i) /ʃ/ in the Goidelic languages begin with
h in the Brythonic languages. For example, old is sean in Irish and
hen in Welsh.
Here is an illustration of some of the differences and similarities between
the Celtic languages using the phrases 'What is your name?' and 'My name is ... / I'm ...':
The only word in these examples that is similar in all the languages is name: ainm (Irish), ainm (Scottish Gaelic), ennym (Manx), anv (Breton), hanow (Cornish) and enw (Welsh).
The word for what - Cén (Irish), De (Scottish Gaelic), Cre (Manx), Petra (Breton), Pyth (Cornish) and Beth (Welsh) - illustrates one of the sound differences between the branches of the Celtic languages. In the Gaelic languages, apart from Scottish Gaelic, it starts with C, which is why they are called Q-Celtic languages (this sound is sometimes written with a Q in Manx), while in the Brythonic languges it starts with p or b, which is why they are known as P-Celtic. Both sounds developed from the Proto-Celtic [kʷ].
There are more similarities within each branch of these languages than between the branches (Gaelic and Brythonic), and the Gaelic languages are closer to one another than are the Brythonic languages.
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