This article describes the grammar of the Old Irish language. The grammar of the language has been described with exhaustive detail by various authors, including Thurneysen, Binchy and Bergin, McCone, O'Connell, Stifter, among many others.
Morphophonology
Initial mutations In the system of initial consonant mutations, the initial consonant of a word is modified in one or another way, depending on the nature of the preceding word: la tech "towards a house" vs. fo thech "under a house", i tech "into a house", with the alternation in the initial consonant of tech "house" triggered by the preceding preposition.
There are three types of mutation: Lenition, a weakening of the initial consonant. This generally turns plosives into fricatives, among other effects. Nasalisation, originally a prepending of a nasal consonant to the word, which caused further changes. Aspiration and gemination, causing either gemination of the initial consonant, or the insertion of .
The mutations became an important part of the grammar and remain, with little change, in Modern Irish (see Irish initial mutations). They were often crucial in distinguishing various grammatical forms, which would be homophones if not for the mutations. For example, in the case of the possessive determiner a, only the initial mutation of the following word distinguishes the meanings "his", "her", and "their":
+ Meanings distinguished by initial mutations No change Lenition Nasalization Aspiration/gemination
Another grammatical feature signalled by mutations is relative clause attachment, in which lenition indicates the beginning of a relative clause, often in place of any explicit relative pronoun (although in some cases the verbal ending also changes to a special relative form).
In general, there is no way to predict from the form of a given word the type of mutation that it will trigger. (Note that the spelling of the initial consonant does not always change to indicate mutation in Old Irish although it generally does starting in Middle Irish).
Initial mutations were originally sandhi effects, and depended on the shape of the original final syllable in Primitive Irish. It was grammaticalised by the loss of final syllables in the transition from Primitive Irish to Old Irish. In Old Irish, the process was already grammatical to a large degree, and was limited to applying across words within a single syntactic phrase (e.g. between a noun and a modifying adjective, or between a preposition and the rest of the prepositional phrase). Initial mutations did not apply across phrase boundaries generally, but there are some instances where this does occur in the earliest Old Irish attestations.
Lenition Lenition is the weakening of a consonant according to a particular pattern. It applied to consonants appearing between vowels in Primitive Irish. When a preceding word ended in a vowel, the first consonant of the following word was lenited.
Lenition was not indicated in the spelling except in the case of initial voiceless stops, which were written ph th ch when lenited. In later Old Irish, initial f s come to be written ḟ ṡ when lenited, with a dot (a so-called punctum delens) above the letter.
Lenition occurs after: Certain case forms within a noun phrase, either of the noun or a preceding article or possessive. These include, at least: Nominative and vocative singular of all feminines Dative singular of all genders Nominative, vocative, accusative and genitive dual of all masculines and feminines Nominative, vocative and accusative plural of all neuters (but inconsistently after -a) Certain prepositions Certain conjunctions Certain infixed pronouns
Nasalisation Nasalisation, also known as eclipsis in Modern Irish grammar, is the prepending of a nasal consonant to the word. It was caused by a preceding word ending in a nasal consonant. Due to later changes involving clusters of nasals and other consonants, in particular the coalescing of nasal-stop clusters to voiced plosives (such as > ), nasalisation may also manifest itself as voicing in Old Irish.
Nasalisation was not indicated in the spelling except for initial voiced stops and vowels, where n- is prefixed (m- before b).
Nasalisation occurs after: Certain case forms within a noun phrase, either of the noun or a preceding article or possessive. These include, at least: Nominative, vocative and accusative singular and dual of all neuters Accusative singular of all masculines and feminines Genitive plural of all genders Certain prepositions Certain conjunctions Certain infixed pronouns
Aspiration and gemination Originally two different effects, aspiration and gemination came to be triggered in the same environments and thus can be treated as one type of mutation.
Aspiration involved prepending an additional to a vowel-initial word. It was primarily caused by syllables formerly ending in , which lenited to between vowels. In gemination, an initial consonant was geminated by a preceding word originally ending in , or after a vowel. By analogy, words originally ending in and came to aspiration before vowel-initial words as well.
Gemination was only occasionally indicated, and as geminated consonants were in the process of reducing to single consonants in Old Irish times, the mutation effect itself was waning. Aspiration was not indicated at all.
Aspiration/gemination occurs after: Within a noun phrase, either of the noun or a preceding article or possessive, all forms that end in a vowel but do not trigger lenition or nasalisation. This includes, at least: Genitive singular of all feminines Vocative and accusative plural of all genders Certain prepositions ní and ba
Palatalisation Palatalisation as such is phonological, but it also has a grammatical aspect to it. Certain case forms of nouns automatically trigger palatalisation of the final consonant of a word, as do forms of verbs. Consequently, the quality of the final consonant can often vary between different forms of the same word.
Palatalisation also occurs when a syllable that originally contained a front vowel undergoes syncope.
Palatalisation can sometimes affect the immediately preceding vowel: ía → é. áe, óe → aí, oí. This is purely an orthographical distinction used in normalised spellings for clarity. It is not adhered to strongly in the manuscripts.
Development and restrictions on palatalization The development of palatalization has been traditionally separated into multiple stages. For these rules, original Proto-Celtic a and ā did not count as front vowels. Palatalization occurred when a single consonant, and also homorganic clusters of a nasal consonant followed by a corresponding voiced obstruent, was surrounded by two original front vowels. Hence "carries" from *bereti-s (*eCe eligible) with palatalized r but not "sings" with unpalatalized n from *kaneti-s (*aCe ineligible). Palatalization occurred for single coronal consonants and nd not only preceded by any vowel except á, but also followed by original Proto-Celtic i or ī. This condition may be illustrated by prefixed derivatives of "counting" from Proto-Celtic rīmā. "recounting" from *torīmā displays palatalization of r, but "number" from *adrīmā did not palatalize its r because it was part of an original ineligible consonant cluster. Palatalization of single labial and velar consonants followed by original Proto-Celtic i or ī was blocked when the consonant was preceded by stressed rounded back vowels. Otherwise palatalization also applied. Palatalization of both single consonants and consonant clusters occurred before stressed front vowels.
The consonant cluster cht never palatalized. Whenever palatalization was expected for grammatical or etymological reasons, the palatalization was omitted. For example, the dative singular of the feminine ā-stem dúthracht "wish" was still dúthracht, not *dúthraicht.
Vowel affection Vowel affection is the changing of the height of a vowel to more closely match the height of the vowel in a following syllable. It is similar to Germanic umlaut, but more pervasive. It was originally a relatively automatic process, but because the final vowels were later mostly lost in the transition to Old Irish, the process became unpredictable and grammaticalised. Three different kinds of vowel affection existed in Old Irish, lowering, raising and u-insertion.
Lowering was caused by a (former) low vowel a or o in the following syllable, and affected the underlying short vowels i and u, changing them to e and o respectively. It occurred regardless of the preceding consonants, and was thus rather common.
Raising was the reverse development: when followed by a (former) high vowel, short i or u, in the following syllable, the vowels e and o were changed to i and u. It did not occur in all cases, as it was limited by the intervening consonants. It occurred only when at most one consonant stood between the syllables, and the consonant had to be voiced (this included sonorants). Thus, while the noun cenn was raised to cinn in the genitive singular form (along with palatalisation), ech was not raised and retained its original vowel in its genitive singular form eich .
The underlying vowel of a word remained when the vowel e formerly followed. For example, in masculine o-stems, the vocative singular form had e in the ending, but the other forms had other vowels which caused either raising or lowering. In neuter o-stems, all forms had raising or lowering endings, none originally contained e. This can make it difficult to ascertain what the original underlying vowel was.
U-insertion was a third effect, caused by a (formerly) following u. It involved inserting the vowel u (or o, as an orthographic variant) after an existing vowel, and occurred with the long vowel é and the short vowels a, e and i. The results were as follows: a → au. e → iu if raising can take place, eu/eo otherwise. i → iu. é → éu/éo, sometimes also íu. U-insertion did not necessarily occur in all cases where it might be expected, in particular when the u that might cause the effect was still present. For example, the accusative plural of ech may be euchu/eochu, but echu is also found, lacking u-insertion. For fer, the accusative plural is firu, never *fiuru.
Syncope Syncope of word-medial unstressed short vowels plays an extensive role in derivational morphology in addition to the inflection of Old Irish nouns, verbs, and adjectives. It activates upon attaching a suffix onto a prehistoric stem that would otherwise make the resulting word at least three syllables long.
When syncope occurs, it deletes the vowel of every even-numbered syllable except the last. Deleted vowels subject the consonant clusters consisting of both the consonants before the syncopated vowel and the consonants after it now standing in their place to transphonologization, as Old Irish generalised the palatal or nonpalatal quality across an entire consonant cluster. If an underlying front vowel like /e/ or /i/ was lost, the whole cluster would be subject to palatalization. On the other hand, syncope of other underlying vowels would cause the loss of any palatalization that the consonants in the cluster previously had. This could lead to alternations between palatalisation in the syncopated forms and non-palatalisation in the unsyncopated forms of a word, and vice versa.
For example, the noun dorus "door" originally had a front vowel e in the second syllable (Proto-Celtic *dworestu), but this did not cause palatalisation due to the u-affection of the final vowel. However, when the noun was syncopated in certain case forms, the palatalisation reappeared and spread also to the final s, seen in the genitive singular doirseo and dative plural doirsib .