Ball gazing genitives

O Goireasan Akerbeltz
Am mùthadh mar a bha e 18:45, 29 dhen Iuchar 2019 le Akerbeltz (deasbaireachd | mùthaidhean) (→‎Best bets)
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Well, it's a little more sophisticated - an reliable - than ball gazing but there's always a margin of error. As with the page on predicting plurals and gendering nouns this is work in progress but someone asked for.

Again to quote Captain Barbossa, the following pointers are more like guidelines. Genitives are hard to predict with certainty, but there are some things that can make life easier. Note also that some genitives vary by dialect.

As with plurals, if anyone starts talking at you about first declension, second declension, and so on, just nod politely and - unless you're aiming for a degree in historical linguistics - run. Though technically useful, working off the basis of these old categories requires in-depth knowledge of Old Irish... see what I mean?

As with plurals, irregular nouns are just that, irregular, so you need to learn those. The ones you should learn off as soon as possible are: athair, bean, bó, bràthair, brù, cù, deoch, Dia, druim, duine, Éirinn, fear, fuil, leabaidh, mac, muir, piuthar, sgian, taigh, talamh. There are lots more, but those will do for starters.

Best bets

Your best bets are special endings (in the nominative singular) which generally take specific genitives. These are the most reliable rules for predicting genitives and if a word has such an ending, you should go with the rules for that special ending in preference to more generic rules.


These are agentive endings. Bits that you stick onto another noun to show that someone makes or does something, like -er in English which gives you fish » fisher, wash » washer, clean » cleaner, and so on. Of these, only -(e)ar changes in the genitive, the others all stay the same:

  • cruthaichear » cruthaicheir
  • ùghdar » ùghdair
  • saighdear » saighdeir

Careful, this only works if the noun is made up of a noun plus an ending or a loanword. There are some feminine nouns which aren't "composed" like that which behave differently. As a general rule, if you take away the ending, and what you're left with doesn't make sense, then it's not one of these. For example, with cathair and nathair, if you remove the -air, you're left with cath and nath and which don't make sense because cath and nath don't mean anything on their own. So, it's not nath+air, but just one word. See the next section for more examples.

-air and -ir

If the -air at the end is not the doer/maker ending, then the noun is usually feminine and syncopates its genitive. In short, syncopating means that you lose a syllable so the genitive is -rach:

  • nathair » nathrach
  • acair » acrach
  • litir » litreach

Two common exceptions are

  • màthair » màthar
  • piuthair » peathar

For a bit more on this topic, check this page.


With a masculine noun ending in -ach, the genitive normally is -aich:

  • balach » balaich
  • boireannach » boireannaich

Watch out for a relatively small number of feminine nouns which end in -ach, for example, làrach. On the bright side, their genitive is often -aich or at worst -aiche (which in Hebridean Gaelic gets reduced to -aich anyway...):

  • làrach » làraich
  • gruagach » gruagaich(e)


Ignore gender with this ending as far as genitive marking goes. They don't change these days:

  • achd » achd
  • feachd » feachd
  • éifeachd » éifeachd


These are nice. They're almost all masculine and virtually all take -(a)idh as the genitive if the word consists of noun + adh, meaning that they must have two syllables, at least:

  • atharrachadh » atharrachaidh
  • moladh » molaidh


If you have a feminine noun with the diminutive ending -(e)ag, then the genitive will be -eige:

  • caileag » caileige
  • marag » maraige
  • cuileag » cuilaige

Careful, there are some masculine nouns which look like they have a diminutive ending -(e)ag at the end, in particular aiseag, but that's not a diminutive ending. Usually, the genitive is close though: -eig (» aiseig).


Also fairly predictably, words ending in -eal turn to -eil in the genitive:

  • caisteal » caisteil
  • inneal » inneil


If you have a masculine noun ending in the diminutive ending -(e)an, then the genitive is normally -ain/-ein.

  • balachan » balachain
  • corran » corrain
  • cuman » cumain
  • cuilean » cuilein
  • ballan » ballain


These are nice. Almost all are masculine and are -(e)is as the genitive:

  • solas » solais
  • carthannas » carthannais
  • doras » dorais


This seems an exotic rule but there are actually many words in this category and something slightly weird happens, so it's useful to know. If a word with one syllable ends in -oc then the genitive will be -uic:

  • cnoc » cnuic
  • broc » bruic
  • sloc » sluic


Let's say there's a tendency for words ending in -th to have -a as a plural:

  • guth » gutha
  • gath » gatha
  • bùth » bùtha

There is a fair number of flies in the ointment, like gaoth » gaoithe

Less reliable stuff


A lot of loanwords don't do genitive marking at all:

  • càr » càr
  • bàr » bàr
  • clas » clas
  • bus » bus

Monosyllables with ia and eu

If you have a word with only one syllable and the vowel is -ia- or -eu- the the genitive is very often -éi-, with feminine nouns also slapping on the final -e

  • ceum » céim
  • fiadh » féidh
  • fiach » féich
  • grian » gréine

Monosyllables with long vowels

If you have a word with only one syllable and the vowel is long, then the genitive very often does something weird to the vowel.

Long -(e)ò- is semi-reliably -(i)ùi- in the genitive:

  • bòrd » bùird
  • ceòl » ciùil

With others, it's less predictable (e.g. ceàrd » ciùird or càrn » cùirn) but even just knowing to expect this weird stuff in this category of noun can help a bit.

When all else fails...

Unfortunately this rule is often taught first, rather than last... Only apply this when none of the above applies, no shortcuts!!!

If the ending in the nominative is broad, the genitive will have a tendency to slenderise it, irrespective of gender, with feminine nouns tending to slap on a final -e but not always.

Beagan gràmair
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