Irish and Welsh are the most spoken Celtic languages. The other Celtic languages —which include Breton, Scottish Gaelic, Cornish, and Manx— have fewer speakers.
Irish has close to 2 million speakers, most of whom are in the Republic of Ireland; Welsh has about 1 million speakers, and most reside in Wales.
Irish and Welsh are both Celtic languages, which may lead one to think that they are very similar. However, this is not the case because they belong to different subgroups within the Celtic language family.
A comparison of the most common Irish words and the corresponding Welsh words shows substantial differences in basic vocabulary.
For ease of comparison, a sample of Irish and Welsh vocabulary words are presented side by side in the table below:
| Irish | Welsh | English |
|---|---|---|
| teanga | iaith | language |
| grá | cariad | love |
| sonas | hapusrwydd | happiness |
| cara | ffrind | friend |
| gealach | lleuad | moon |
| grian | haul | sun |
| abhainn | afon | river |
| sliabh | mynydd | mountain |
| báisteach | glaw | rain |
| baile | tref | town |
Welsh and Irish have substantial differences in vocabulary because they belong to separate branches within the Celtic language family. Welsh, Breton, and Cornish are Brythonic languages. Irish, Scottish Gaelic, and Manx are Goidelic languages.
Celtic languages within the same group have more similarities in vocabulary.
For example, the Welsh word “cariad” and the Irish word “grá” both mean “love”, but they are very different. Yet, the Welsh word “cariad” resembles the Breton verb “karout,” which means “to love.” That’s because Breton and Welsh are both Brythonic languages.
The Irish word “grá” is similar to the Scottish Gaelic term “gràdh”, which also means “love”. This similarity reflects the fact that Irish and Scottish Gaelic are both part of the Goidelic group of Celtic languages.
Some examples of similar Irish and Welsh vocabulary words are listed in the table below. Most of these are cognates (they have the same origin).
| Irish | Welsh | English |
|---|---|---|
| milis | melys | sweet |
| dorn | dwrn | fist |
| carraig | carreg / craig | rock |
| dubh | du | black |
| neart | nerth | strength |
| garbh | garw | rough |
| lán | llawn | full |
| tine | tân | fire |
| cluas | clust | ear |
| lámh | llaw | hand |
| bolg | bol | stomach |
Some linguists classify Celtic languages into two groups: the P-Celtic languages (which include Welsh) and Q-Celtic languages (which include Irish).
This classification is based on a sound change that occurred as the Celtic languages evolved from the Proto-Celtic language. (The Proto-Celtic language is the ancestor of all Celtic languages. It is a language that has been reconstructed by linguists.)
The Proto-Celtic phoneme kʷ generally evolved into a ‘p’ sound among the P-Celtic languages. And it often evolved into a ‘q’ sound among the Q-Celtic languages.
This explains why many Irish words have the letter ‘c’ while the corresponding Welsh word has the letter ‘p’ instead. Some examples are listed in the table below:
| Irish | Welsh | Proto-Celtic |
|---|---|---|
| ceathair (four) |
pedwar (four) |
*kʷetwares (four) |
| cúig (five) |
pump (five) |
*kʷenkʷe (five) |
| ceann (head) |
pen (head) |
*kʷennom (head) |
| cé (who) |
pwy (who) |
*kʷēs (who) |
| ciall (sense) |
pwyll (sense) |
*kʷēslā (mind, sense) |
| coire (cauldron) |
pair (cauldron) |
*kʷaryos (cauldron) |
| cuid (part) |
peth (thing) |
*kʷezdis (part) |
| cad (what) |
pa (which) |
*kʷid (what) |
| crann (tree) |
pren (tree, wood) |
*kʷresnom (tree, wood) |
| cruimh (worm) |
pryf (worm) |
*kʷrimis (worm) |
| crean (to buy) |
prynu (to buy) |
*kʷrinati (to buy) |
| cré (clay) |
pridd (clay, soil) |
*kʷrīyess (clay) |
| mac (son) |
mab (child) |
*makʷos (son) |
| aitheasc (a speech) |
ateb (answer) |
*sekʷeti (to say) |
| fliuch (wet) |
gwlyb (wet) |
*wlikʷos (wet) |
Many Welsh words start with the letter combination ‘gw’, for instance, the popular Welsh name Gwyneth. (for more examples see these articles on Welsh girl names and Welsh boy names)
Many Irish words start with the letter ‘f’, for example, the name Fiona which comes from the Irish word « fionn » meaning “fair” or “blond”. (see these articles on Irish girl names and Irish boy names)
The Welsh name Gwyneth and the Irish name Fiona look very different, but they originate from the same Proto-Celtic root.
The Proto-Celtic term « windos » is the origin of the Welsh word « gwyn » which means “white” or “blessed”. It is also the origin of the Irish word « fionn ».
The difference is due to a consonant shift: the letter ‘w’ at the beginning of Proto-Celtic words became ‘gw’ in Welsh, and it became ‘f’ in Irish.
Here are more Welsh and Irish word pairs which illustrate this shift:
| Irish | Welsh | Proto-Celtic |
|---|---|---|
| fear (man, husband) |
gŵr (man, husband) |
*wiros (man, husband) |
| féar (grass) |
gwair (grass) |
*wegrom (grass) |
| fíor (true) |
gwir (true) |
*wīros (true) |
| faoileán (seagull) |
gwylan (seagull) |
*wēlannā (seagull) |
| fleá (feast) |
gwledd (feast) |
*wlidā (feast) |
The vocabulary of Irish and Welsh exhibits significant differences, to the extent that even cognate words —those that have a common origin— can be challenging to identify without a thorough understanding of the linguistic transformations that took place as these languages evolved from their Proto-Celtic ancestor.
Welsh is closer to Breton (which is also in the Brythonic group of Celtic languages) than it is to Irish.
Irish is closer to Scottish Gaelic (which is also in the Goidelic group of Celtic languages) than it is to Welsh.
To further compare Welsh and Irish (and to learn some basic phrases in these languages), see these three articles covering Basic Welsh Phrases for Beginners, Welsh compliments, and Irish compliments.
For an overview of Celtic languages, see this article on the easiest and the hardest Celtic languages.