Caibidil a hAon: The Noun (an tAinmfhocal)

Firinscneach agus baininscneach

Basically, those living things which are male are named with masculine nouns, for female creatures then feminine nouns.
There are definite exceptions to the rule: e.g.: stail  = stallion is feminine, cailín = girl is masculine (about the suffix -ín see below)
For all inanimate objects: Belonging to one group or another is mostly random, or. dependent on the ending (see below)
In this way, Irish is quite similar to German, with the difference that Irish has no "thing" gender (neutrum) anymore.

where are the differences between the genders?

• in the use of the definite article in the nominative and genitive, including the following initial mutations.
  (an or na, lenition or nor, t-prefix preceding s and vowels or not)
• in the lenition and declension of the following adjectives
• in the use [ 1 ] pf the personal pronoun (he = sé or she = sí) and the possessive pronoun (his / her = a with lenition / without lenition) as well as the prepositional pronouns (e.g.aige = by him, aici = by her, as = out of him, aisti = our of her)

how does one recognise the gender of a word?

• all of the 1st declension , most of the 4th declension
• except im, sliabh, teach none of the 2nd declension, only a few of the 5th declension
• most professions
• words with the following endings:
  • all those ending in -adh, -amh, -aí, -án, -ar, -aire, -as, -éara, -aeir, -éir, -eoir, -óir, -úir, -éad, -ste, -ú, -ún [ 2 ], -úr [ 2 ]
  • words ending in -ín (see diminutive)
  • bisyllabic words ending in -a (e.g.: mála = bag, muga = mug )
  • monosyllabic words ending in -cht (e.g.: lucht = charge, group, reacht = right, bocht = poor person )
  • derivatives using -ach (e.g.: Éire = Ireland > Éireannach = Irishman, Gearmánach = German, Sasanach = Englishman, Caitliceach = Catholic )

• all of the 2nd declension (except: im,sliabh,teach), most of the 5th declension
• none of the 1st declension, only a few of the 4th declension
• all country names (except: Sasana, Ceanada, Meiriceá), languages (exception Béarla), rivers
• words with the following endings:
  • all those ending in -áil, -aíl, -eog, -óg, -seach, -lann, -íocht
  • polysyllabic words ending in -acht (e.g. Gaeltacht)
  • all those ending in -ach, except derivatives (e.g. báisteach = rain )

the diminutive suffix (iarmhír an dhispeagtha) -ín

diminutive = pet form

The suffix -ín is the same as the German -chen or -lein (fear = man > firín = little man)
Words ending in -ín (4th declension) are actually masculine.
Basically, masculine are those words, that in the diminutive are no longer able to be taken as the root meaning or those that take on a whole new meaning.
(e.g. "cailín" is not the diminutive of the archaic "caile", just as little as the "Mädchen" is still seen as the diminutive of "Maid". This is why "cailín = girl " is masculine!)

In the case of a real diminutives (an díspeagadh) it's a bit more complicated:

• if the base word is masculine then the diminutive is also masculine
  (e.g.: an firín = the little man, an leabhairín = the booklet )
• if the base word is feminine, then:
  • the nominative singular is seen as feminine
    (e.g.: an pháirc bheag = the little park > an pháircín bheag = the little mini-park )
  • the genitive singular is seen as masculine
    (e.g.: cranna na páirce bige = the trees of the little park> cranna an pháircín bhig = the trees of the little mini-park )
  • in the plural the gender is not recognisable
    (e.g.: na páirceanna beaga = of the little parks > na páircíní beaga = the little parks )
• by female personal names, the diminutive is always feminine (Brídín, Nóirín)

Side note : Today only the suffix -ín used to produce the diminutive . Earlier one used further suffixes as well, e.g. -óg (feminine), -án (masculine), e.g. cnocán = a little hill, eitleog = a little flight , ordóg = thumb (= "little hammer ")

Fußnoten:
[ 1 ]:masculine words denoting people with a naturally feminine gender may still use the feminine pronoun (an cailín > sí, í) (and the other way around). But still some noun and pronoun genders do not agree (see personal pronouns)
[ 2 ]: -ún, úr: also words stemming from Latin, there feminine, are masculine in Irish: an naisiún = the nation, an nadúr = nature