Some Diagnostic Features of Middle Irish

A friend of mine, with whom I am teaching Old Irish, asked for some diagnostic features of Middle Irish so I thought I would put it here to help them and anyone else who may want to know.


There are many different features which mark the change from Old to Middle Irish. Much of this is discussed in much more detail in Kim McCone’s “A First Old Irish Grammar and Reader” pp. 173—217. I will give a small précis of this here. For a more full account for verbs, see Kim McCone “The Early Irish Verb” pp. 163—240. A full analysis by Liam Breatnach is detailed in “Stair na Gaelige” pp. 221—333. The main problem with Breatnach’s analysis is that it is entirely in Modern Irish so unless you know that language first, or you enjoy typing and trust Google Translate, it will be inaccessible to you.

Loss of Final syllables

In some noun classes, you will notice a loss of final syllables or they will fall into ə (schwa). The canonical example is daltae (fosterling, later student) in the nom. and acc. will become dalta. If you check Thurysen “Grammar of Old Irish” pg. 179, you will notice that the a in daltae is optional, which is marked dalt(a)e. In Middle Irish, the e is lost and the a is mandatory. This will also happen in verbs that end in -ae more generally.

Verbal system reordered

The deutertonic forms of compound verbs disappear and they are re-analysed as their prototonic forms with weak simple verb endings. For instance, do-léici “casts/throws” becomes teilg(eann) from the prototonic form -teilci (he casts). In a sentence, you may see this teilgam “I cast” for Old Irish do-léiciu (or do-léicim). In addition, the deponent verbs also disappear entirely and are re-analysed in the same way as the compound verbs. In the future tense, the f-future becomes the norm, as it is in Modern Irish.


The infixed pronoun completely disappears, are confused, or petrified. They are replaced by the independent pronoun. For instance, a very common petrification is at-beir “he says it” for “he says” with obvious object or object pronoun for the verb. For instance, at-beir-som rúin frisin ingin “he says a secret to the girl”. The infix pronoun at- is not necessary and just means “he says [it] a secret to the girl”. Please also note that the emphatic -som is the only way to tell if it is “he” rather than “she” in Old Irish which is why, when loss of final syllables like above occur, the independent pronoun is pressed into service.

Loss of the Neuter Gender

The neuter gender for all noun classes disappear and become masculine.

Relative Clauses

The leniting and nasalizing relatives clauses disappear to be replaced with relative marker “a”.

Loss of the Equitive and other adjectival changes

The comparative of adjectives are generally used in Old Irish with the verbal construction ol-daas (or placed in the dat.), which means “than it is”, notice the hiatus here (see Thurysen GOI pp. 477—478 and pg. 232). This becomes petrified and begins breaking down. Ol-daas becomes naas then later níos and ná in Modern Irish. For example, feicfidh mé thú níos déni in Modern Irish (I will see you later).

Orthographic Changes

So far, you will not notice much in the way of spelling changes. What you will notice is that beginning and medial c becomes g. So, cach becomes gach, oc becomes ag, ocus comes agus, which are the same as in Modern Irish.

These are the most notable changes from Old to Middle Irish. The references at the beginning will refine and explained these so I would recommend you read those as well as this.

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