Irregular Nouns
A guide to the most common Irish nouns with irregular declensions, including their case forms and historical notes.
While most Irish nouns follow one of the five standard declensions, a small group of very common nouns have unique, irregular forms that must be learned individually. A noun is typically classified by its genitive singular form, but these nouns resist easy classification. This page covers the most frequent irregular nouns you will encounter.
Core Irregular Nouns
Bean (woman)
This is one of the most common and most irregular nouns in Irish.
| Case | Singular | Plural |
|---|---|---|
| Nominative | an bhean | na mná |
| Genitive | na mná | na mban |
| Dative | an mhnaoi | na mná |
- Tá bean sa ghairdín. - There is a woman in the garden.
- Hata na mná. - The woman’s hat.
- Thug sé an leabhar don mhnaoi. - He gave the book to the woman.
Historical note
The old dative plural form was mnáibh, which is now archaic.
Deirfiúr (sister)
The word for a female sibling is highly irregular.
| Case | Singular | Plural |
|---|---|---|
| Nominative | an deirfiúr | na deirfiúracha |
| Genitive | na deirféar | na ndeirfiúracha |
| Dative | an deirfír | na deirfiúracha |
- Sin í mo dheirfiúr, Síle. - That is my sister, Síle.
- Ainm mo dheirféar ná Aoife. - My sister’s name is Aoife.
Etymology
The word deirfiúr was formed with the prefix deirbh- (“true” or “of the same blood”) to distinguish a biological sister from a siúr (a religious sister or nun). The f comes from the lenition of s in the Indo-European root swesor, which is also the root of the English word “sister”.
Siúr (sister, nun)
This word refers to a religious sister or nun.
| Case | Singular | Plural |
|---|---|---|
| Nominative | an tsiúr | na siúracha |
| Genitive | na siúrach | na siúracha |
- Is siúr í i gclochar i mBaile Átha Cliath. - She is a nun in a convent in Dublin.
Dia (God)
The word for God has a distinct genitive form.
| Case | Singular | Plural |
|---|---|---|
| Nominative | Dia / an dia | na déithe |
| Genitive | Dé / an dé | na ndéithe |
- Grásta Dé. - The grace of God.
- Scéalta faoi na déithe. - Stories about the gods.
Lá (day)
This common noun has a distinct dative form, ló, which is often seen in set phrases.
| Case | Singular | Plural |
|---|---|---|
| Nominative | an lá | na laethanta |
| Genitive | an lae | na laethanta |
| Dative | an ló | na laethanta |
- Lá breá gréine a bhí ann. - It was a fine sunny day.
- Ag deireadh an lae. - At the end of the day.
- Oibríonn sé i rith an lae agus codlaíonn sé i rith na hoíche. - He works during the day and sleeps during the night.
Leaba (bed)
| Case | Singular | Plural |
|---|---|---|
| Nominative | an leaba | na leapacha |
| Genitive | na leapa | na leapacha |
- Tá an leabhar ar an leaba. - The book is on the bed.
- Cos na leapa. - The leg of the bed.
Historical forms
The genitive leapa likely arose from an older form leabtha. Other historical variants for the genitive include leapan, leaban, and leabadh.
Mí (month)
| Case | Singular | Plural |
|---|---|---|
| Nominative | an mhí | na míonna |
| Genitive | na míosa | na míonna |
- Tá dhá mhí dhéag sa bhliain. - There are twelve months in the year.
- Ag tús na míosa seo chugainn. - At the start of next month.
Olann (wool)
| Case | Singular | Plural |
|---|---|---|
| Nominative | an olann | na holanna |
| Genitive | na holla | na n-olann |
- Tá an geansaí seo déanta as olann. - This jumper is made of wool.
- Praghas na holla. - The price of wool.
Historical note
Although it appears irregular, olann can be seen as a regular 3rd declension noun. The genitive olla comes from syncope (loss of a vowel) in the older form olna, where the ln sound combination evolved into ll.
Talamh (land, ground)
| Case | Singular | Plural |
|---|---|---|
| Nominative | an talamh | na tailte |
| Genitive | na talún | na dtailte |
- Cheannaigh siad píosa talún. - They bought a piece of land.
- Tá na tailte sin an-torthúil. - Those lands are very fertile.
Historical forms
The genitive talún is consistent with the 5th declension; the older spelling was talmhan. There is also a regular 1st declension masculine variant: talamh (nom. sg.), talaimh (gen. sg.).
Ó / Ua (grandson, descendant in names)
This element, common in surnames, has its own declension.
| Case | Form | Example |
|---|---|---|
| Nominative | Ó / Ua | Pádraig Ó Súilleabháin |
| Genitive | Uí | Bean Uí Shúilleabháin (Mrs. O’Sullivan) |
| Vocative | Uí | A Uí Shúilleabháin! (Mr. O’Sullivan!) |
Micheál (Michael)
Like many proper names, Micheál has an irregular genitive.
| Case | Form |
|---|---|
| Nominative | Micheál |
| Genitive | Michíl |
- Sin é carr Mhichíl. - That is Michael’s car.
Nouns Sometimes Classed as Irregular
Some nouns have highly distinct forms but can technically be assigned to a standard declension, usually the 2nd.
Teach (house)
| Case | Singular | Plural |
|---|---|---|
| Nominative | an teach | na tithe |
| Genitive | an tí | na dtithe |
| Dative | an tigh | na tithe |
- Tá an teach mór. - The house is big.
- Doras an tí. - The door of the house.
- Tá sé sa tigh. - He is in the house.
Deoch (drink)
| Case | Singular | Plural |
|---|---|---|
| Nominative | an deoch | na deochanna |
| Genitive | na dí | na ndeochanna |
| Dative | an digh | na deochanna |
- Ba mhaith liom deoch uisce. - I would like a drink of water.
- Blas na dí. - The taste of the drink.
Nouns with Irregular or Variant Forms
Bia (food)
In the standard language, bia is a regular 4th declension noun, with bia for both nominative and genitive singular. However, older forms are still common in some dialects.
- An bhfuil an bia réidh? - Is the food ready?
Bó (cow)
This noun is now mostly regular (4th declension), with the main exception being its very short plural form.
| Case | Singular | Plural |
|---|---|---|
| Nominative | an bhó | na ba |
| Genitive | na bó | na mbó |
- Tá an bhó sa pháirc. - The cow is in the field.
- Tá na ba ag ithe féir. - The cows are eating grass.
Historical forms
An older dative singular form, boin, placed this noun closer to the 5th declension. The old dative plural was buaibh.