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The Genitive in Irish Grammar

When people first start studying the Irish language, they very quickly run up against concepts they’ve never encountered before. For many, the most daunting is a special form of the noun known as “the genitive case.”

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There are several ways to form the genitive in Irish, depending on such factors as the gender, number, and declension of the noun.  That’s really beyond the scope of a single blog post.  If you’re learning Irish, your teacher, book, or program should help with that.

If you’re a Bitesize Irish Gaelic member, you can access these lessons on the genitive, complete with audio, via the following links:

What this post will discuss, rather, is some of the ways the genitive is used in the Irish language, and why it’s so important to get a handle on it.

First, a couple of terms

It’s impossible to discuss grammar without using a few specialized terms. Here are a few that I’ll be using in this post:

Noun: A word that refers to a person, a place, or a thing.  “Dog,” “teapot,” “man,” and “Dublin” are all nouns.

Adjective: A word that describes a noun or pronoun. “Ugly,” “funny,” “cold”, and “pretty” are all adjectives.

Case: A special form a noun or adjective can take that indicates its relationship to the other words around it.

How the genitive is used in Irish

The genitive case is used a lot in Irish. Three of the most common uses are:

  • To show possession
  • In a place where “of” would be used in English
  • To turn a noun into an adjective.

Using the genitive to show possession

In English, if we want to say that something belongs to someone, we use an apostrophe followed by  the letter “s”:

Seán‘s house

The man‘s hat

If we’re talking about multiple owners, we use put the apostrophe after the letter “s”:

The Murphys’ boat

In Irish what we do instead is put the word that represents the owner(s) into the genitive case and put it AFTER the word for the thing that is owned: For example:

Seán = Seán and teach = house, but teach Sheáin = Seán’s house

Hata = hat and an fear = the man, but hata an fhir = the man’s hat

Ó Murchú = Murphy and bád = boat, but bád Uí Mhurchú = the Murphys’ boat

“Sheáin,” “an fhir,” and “Uí Mhurchú” are the genitive forms of “Seán,” “an fear,” and “Ó Murchú.”

In place of “of”

The genitive case is often used in Irish where we would use the word “of” in English. One of the easiest ways to show how this works is through Irish surnames.

You probably already know that the “Mac” (sometimes Anglicized to “Mc”) in an Irish surname means “son.” You may not know that the “Ó” (usually Anglicized to “O'”) means “grandson/descendent.”

All native Gaelic surnames originally meant “son/descendent of [a man’s given name, nickname, or occupation].” Instead of using a word for “of,” however, Irish puts the name, nickname, or occupation in the genitive case. For example:

Mac = SonAodh = A man’s nameMac Aoidh = Son of Aodh: The Irish form of “McKay” or “McKee.”

Ó = Grandson/descendentGabha = Blacksmith.  Ó Gabhann Grandson/descendent of a Blacksmith: The Irish form of “Gowen” or “Going.”

When a noun becomes an adjective

We use nouns as adjectives (that is, as words that describe another noun) all the time in English. For example:

Butter knife

Fire extinguisher 

In the above examples, “butter” and “fire” are nouns acting as adjectives, because they describe what kind of “knife” or “extinguisher” we’re talking about.

In Irish, though, we can’t just put one noun in front of another as we do in English. What we do instead is take the first noun, put it in the genitive case, and then move it after the word it describes, which is where adjectives are placed in Irish:

Scian = knife.  Im = butter.  Scian ime = butter knife.

Múchtóir = extinguisher.  Dóiteán = fire.  Múchtóir dóiteáin = fire extinguisher.

“Ime” and “dóiteáin” are the genitive forms of “im,” and “dóiteán.”

Did you find this post helpful?

Did this post help you understand the importance of the genitive case in Irish grammar? Let us know by posting a comment below.

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21 thoughts on “The Genitive in Irish Grammar”

  1. I would love to see a flow chart of how you break down deciding if it is genitive plural or singular. I know you at this point have muscle memory so do not break it down in a step by step decision, but to build my own muscle memory it would be helpful if I do.
    Example if I see the na that is being the owner, what questions do I ask myself to decide if this is owner single or owner plural, such as do I discern if it is masc or fem and if so, what general tips will I use to decide that?
    If I had this break down, I would put it in an actual flow chart and share.

  2. What about when you have two nouns. Eg: “He is a man of the house and the town.” (Not a great example but you know what I mean.) Is it “is fear an tí agus an bhaile é”, or “is fear an tí agus an baile é”? I’m wondering if it’s only the first noun (tí) which takes the genitive case?

  3. Hi,
    I’m surprised, I always thought Ó Murchú came from Óg as in ‘young Murphy down the road’.
    GRMA for all the work ye’re doing.
    à Mhàire

  4. So, what about non-Irish pronouns? Is there a method to determine what the genitive case of any hypothetical word?
    Go raibh mhaith agat

    1. Sorry, I just now realised I meant “non-Irish proper nouns”. Sorry for any inconvenience.
      Go raibh mhaith agat

    2. Hi Ben,

      Thank you for your comments.

      Generally, it is advised to add “a” before a non-Irish proper name in the vocative case eg. “a John”. You may also find that many people also add Irish grammatical rules eg. “a Bheatrice”.

      Gender usually depends on the ending of the word, therefore, you can sometimes tell from the last few letters in a word. Examples are “-ín” (masculine), “-eog/-óg” (feminine), “-lann” (feminine). You will learn this by searching as many words as possible in the dictionary (www.teanglann.ie) and seeing the patterns develop.

      Le meas,

      1. As a general principal if the noun is broad (the last vowel is a,o,u or á,ó,ú) it is masculine and if it is slender (i,e or í, é) then it is feminine. There are some exceptions like -óg/-eog or -lann is feminine but the rule mostly holds true.

  5. I’m new to this, as I’ve spent an hour/day for the last 3 weeks looking at YouTube, BiteSize, etc. I found this page (http://bitesize.irish/blog/genitive-case-irish/) VERY helpful because it provides a hard and fast rule that I can use relative to “possession”. Maybe it is beyond the scope of this website, but a link to how words are transformed into genitive would be helpful (maybe already there?). I’ve noticed that books (dictionary and grammar) and websites consistently give lots of examples but few rules (still new here). I find such an approach to be counter intuitive to breaking down a problem in order to solve it. Eoin’s Bitesize pronunciation class was very helpful as was Karen Reshkin’s YouTube video on sounds/spelling.

  6. patrick mc nally

    Just a short note Audrey, If “Garda Síochána” can be classed as another example I can seehow they are using The Genitive Case more clearly in this example than in the previous one. Pádraig

  7. patrick mc nally

    I was wondering if “Timpiste Bóthar” could be classed as a noun used as an adjective. Padraig

      1. “Ime” and “dóiteáin” are the genitive forms of “i,” and “dóiteán.” Should be ‘im’.

        Timpiste bhóthair perhaps? I’m not sure, and this is a tricky area with all kinds of exceptions. Áit dhúchais is another example (and since the noun dúchas is functioning as an adjective, the DNTLS rule doesn’t apply).