The first declension

From a mixture of the excellent Basic Irish Workbook by Nancy Stenson and the also surprisingly good wikipedia page

en.wikipedia.org/wiki/Irish_declension

here is a description of the first declension.

1st declension: Masculine nouns ending in a broad consonant which is made slender in the genitive. In the usual way there are weak plurals and strong plurals. In a weak plurals the plural nominative is different from the plural genitive. I imagine there are a few exceptions, but in general weak plurals are only found in the 1st declension!

1st declension weak: Typically in the first declension for a weak plural the plural goes the other way to the singular: the plural is slender but reverts to broad in the genitive. A well behaved example is bád:

singular bád → báid, plural báid → bád

With repeated vowels there can be more complex changes related to the slenderization:

singular fear → fir, plural fir → fear

singular iasc → éisc, plural éisc → iasc

Here are some more regular examples:

• singular cnoc → cnoic, plural cnoic → cnoc - hill

• singular port → poirt, plural poirt → port - port or landing place

• singular corp → coirp, plural coirp → corp - body

• singular poll → poill, plural poill → poll - hole

• singular bolg → boilg, plural boilg → bolg - belly

and nearly regular:

• singular dorn → doirn, plural doirne → dorn - fist

Here are some more examples where slenderizing causes larger changes:

• singular mac → mic, plural mic → mac - son

• singular ceann → cinn, plural cinn → ceann - head

There are also examples that form the plural using -a, the obvious example is úll:

• singular úll → úill, plural úlla → úll - apple

and here are two more examples:

• singular ceart → cirt, plural cearta → ceart - a right

• singular cleas → clis, plural cleasa → cleas - a trick

1st declension strong: here the genitive is in the singular is still formed by slenderising, but the plural is formed by adding something, such as -(e)anna and the genitive has the same form as the nominative, obviously.

• singular carr → cairr, plural carranna - a car

• singular néal → néil, plural néalta - a cloud

• singular scéal → scéil, plural scéalta - a story

and, as happens so often -ach changes to -aigh:

• singular éadach → éadaigh, plural éadaí - a cloth

• singular aonach → aonaigh, plural aontaí - a fair

• singular bealach → bealaigh, plural bealaí - a way

With an article: these are masculine nouns so the usual rules apply, in the singular genitive the article remains an, there is a séimhiú: cat an fhear , the man’s cat, and a t before an s but nothing in front of a vowel: hata an éisc, the fish’s hat. In the plural the article is na and there is úru, dáthanna na gcarranna, the cars’ colours, with a n- before a vowel: hatanna na n-iasc, the fishes’ hats.

History: obviously this would be interesting, I don’t know. I don’t know if Irish declensions map on to Latin declensions through some common origin in proto-whatever. There isn’t any obvious story here with cognates, fear is cognate with vir, a second declension noun, but corp is cognate with corpus, a third declension Latin noun, as is pisces, which is cognate with iasc, so who knows. I assume these words all had some ending that changed for case and these endings disappeared but reflecting this obsession Irish speakers of 600 seem to have had with things sounding nice, the endings left behind vowel-harmony type changes to the stems that came to stand in for the endings now lost.