Old Irish was affected by a series of phonological changes that radically altered its appearance compared with Proto-Celtic and older Celtic languages (such as Gaulish, which still had the appearance of typical early Indo-European languages such as Latin or Ancient Greek). The changes occurred at a fairly rapid pace between 350 and 550 CE.
Summary of changes
A capsule summary of the most important changes is (in approximate order):
Syllable-final (from PIE , ) assimilated to the following phoneme, even across word boundaries in the case of syntactically connected words. Voiceless stops became voiced: > . Voiced stops became prenasalised . They were reduced to simple nasals during the Old Irish period. Before a vowel, was attached to the beginning of the syllable. Lenition of all single consonants between vowels. That applied across word boundaries in the case of syntactically connected words. Stops became fricatives. became (later lost unless the following syllable was stressed). was eventually lost (much later). became a nasalised continuant (; perhaps or ). remained, but the non-lenited variants were strengthened to (see Old Irish phonology). Extensive umlaut ("affection") of short vowels, which were raised or lowered to agree with the height of following Proto-Celtic vowels. Similarly, rounding of to or often occurred adjacent to labial consonants. Palatalization of all consonants before front vowels. Loss of part or all of final syllables. Loss of most interior vowels (syncope).
They led to the following effects: Both the palatalised ("slender") and lenited variants of consonants were phonemicised, multiplying the consonant inventory by four (broad, broad lenited, slender, slender lenited). Variations between broad and slender became an important part of the grammar: in masc. -stems: "son" (nom. acc.) vs. (gen.), "back" (nom. acc.) vs. (gen.), cf. Latin (nom.), (acc.) vs. (gen.); in fem. -stems: "tribe, people" (nom.) vs. (acc. dat.), "pig" (nom.) vs. (acc. dat.); in -stems: "father" (gen.) vs. (nom. acc. dat.). Lenition and nasal assimilation across word boundaries in syntactically connected words produced extensive sandhi effects (Irish initial mutations). The variations became an important part of the grammar. Both umlaut (vowel affection) and especially syncope radically increased the amount of allomorphy found across declensions and conjugations. The most dramatic deviations are due to syncope: compare "they say" vs. "they do not say" or "he surpasses" vs. "he does not surpass" (where the stressed syllable is boldfaced).
Syncope in detail In more detail, syncope of internal syllables involved the following steps (in approximate order): Loss of most final consonants, including , , , , , and all clusters involving (except , , where only the is lost). Loss of absolutely final short vowels (including those that became final as a result of loss of a final consonant and original long final vowels). Shortening of long vowels in unstressed syllables. Collapsing of vowels in hiatus (producing new unstressed long vowels). Syncope (deletion) of vowels in every other interior unstressed syllable following the stress. If there are two remaining syllables after the stress, the first one loses its vowel; if there are four remaining syllables after the stress, the first and third lose their vowel. Resolution of impossible clusters resulting from syncope and final-vowel deletion: Adjacent homorganic obstruents where either sound was a fricative became a geminate stop, voiceless if either sound was voiceless (e.g. > ; etc. > ). Otherwise, adjacent obstruents assumed the voicing of the second consonant (e.g. > ; > ; > ). not adjacent to a vowel became syllabic and then had a vowel inserted before them (e.g. "world" < < < ; "sin" < ). However, in the case of , that occurred only when the nasal had not previously been joined to a following voiced stop as a result of nasal assimilation: compare "present" (disyllabic). Remaining impossible clusters were generally simplified by deletion of consonants not adjacent to vowels (such as between other consonants). However, Old Irish tolerated geminates adjacent to other consonants as well other quite complex clusters: "name" (one syllable), "widow", "they are shown".
Changes to Proto-Celtic stressed short vowels
All five Proto-Celtic short vowels (, , , , ) survived into Primitive Irish more or less unchanged in stressed syllables.
During approximately A.D. 450-550 (just before the Old Irish period, c. 600-900), however, there occurred several vowel-changes (umlauts). Former vowels are modified in various ways depending on the following vowels (or sometimes surrounding consonants). The mutations are known in Celtic literature as affections or infections such as these, the most important ones: -affection: Short and are raised to and when the following syllable contains a high vowel (, , , ). It does not happen when the vowels are separated by voiceless consonants or certain consonant groups. -affection: Short and are lowered to and when the following syllable contains a non-high back vowel (, , , ). -infection: Short , , are broken to short diphthongs , , when the following syllable contains a or that was later lost. It is assumed that at the point the change operated, -vowels that were later lost were short while those that remain were long . The change operates after -affection so original may end up as .
Nominal examples (reconstructed forms are Primitive Irish unless otherwise indicated):
+ Word Form Derivation Affection "old" nom. sg. < gen. sg. < i‑affection dat. sg. < < < PIE i‑affection & u‑affection acc. pl. < i‑affectionno u‑affection because u remains "man" nom. sg. < < a‑affection gen. sg. no a‑affection dat. sg. < < < PIE u‑affection acc. pl. < < PIE no u‑affection because u remains "strength" nom. sg. dat. sg. < < < PIE u‑affection, but i‑affection blocked by the cluster "honey" nom. sg. < i‑affection "sweet" adj. < i‑affection "miracle"nom. sg.< < Latin u‑affection nom. pl. < a‑affection
Before i-affection occurred, there was also a lowering of initial-syllable Proto-Celtic e to a before palatalized reflexes of , unless a followed them in the next syllable in Primitive Irish (no matter the 's origin) which would instead lead to i-affection to i. For instance, Proto-Celtic "(s)he lies" vs. "they lie" vs. "lying" led to a three-way split in Old Irish , , and respectively.
Verbal paradigm example:
{|class="wikitable" ! !! form !! Pronunciation !! Meaning !! Prim Irish !! Post-PIE !! Comments |- | Absolute 1sg || || || "I carry" || || + -s || -affection |- | Absolute 2sg || || || "you (sg.) carry" || || + -s || -affection (unstressed *-es- > *-is- in Primitive Irish, also found in -stems) |- | Absolute 3sg || || || "he carries" || || + -s || Unstressed = with surrounding palatalised consonants; see #Orthography |- | Conjunct 1sg || || || "I carry" || < || || -affection + -affection |- | Conjunct 2sg || || || "you (sg.) carry" || < || || -affection (unstressed *-es- > *-is- in Primitive Irish) |- | Conjunct 3sg || || || "he carries" || < || || in signals palatalisation of following consonant; see #Orthography
The result of -affection and -affection is that it is often impossible to distinguish whether the root vowel was originally or ( < and < have identical declensions). However, note the cases of vs. above for which -affection, but not -affection, was blocked by an intervening .
Complications of u-infection The result of u-infection of *a eventually reduced to /u/ during the Old Irish period. It does not share its later evolution with original *au, which instead became (or broken into ) in Old Irish.
In addition, the u-affection of a when the u preceded a palatalized consonant originally turned the a into an , whose spelling varied among au, ai, i, e, and u depending on the scribe. then spread to various terms prefixed with "fore-" and "ad-".
Stressed front vowels in hiatus Stressed short front vowels in hiatus underwent a loop throughout Primitive Irish and early Old Irish in which they would repeatedly switch between i and e. McCone outlines the loop as follows:
Primitive Irish *e before a hiatus (i.e. over or *y between two vowels) raised to *i before a non-front vowel. Primitive Irish *i before a hiatus then underwent a-affection normally, lowering it down to *e. In early Old Irish, stressed *e before a hiatus raised again to i if the hiatus avoided syncope. If syncope had removed the hiatus, the e was not raised.
Examples of words that went through this loop include: The a-subjunctive paradigm of "to buy". The 3rd-person plural conjunct > > > showcases a full loop. The 3rd-person plural relative > > > shows Step 3 being skipped due to syncope deleting the hiatus that triggered the verb's progress in the loop. The declension of "whitethorn", where Step 1 is inapplicable. The nominative singular > > > > shows apocope destroying a hiatus, leading to Step 3 being skipped. The genitive singular > > > > > shows a completed cycle with Steps 2 and 3 undergone.
Short vowels before nasals and stops Proto-Celtic *a before nasals followed by a stop manifested as the allophone in the prehistory of Irish.
Short vowels and *e, and *i regularly became e before nasals followed by originally voiceless stops, which then lengthened to in stressed syllables. "100" < and "death" < "path, way" < "lets, leaves" < (secondarily transferred to the weak verbs)
But a different development of occurred before nasals followed by voiced stops. According to Schrijver, this became i when affected by i-affection and a when it was not. McCone however instead believes that i was the default outcome of before voiced nasals unless a-affection applied, lowering it down to a. Some examples of these developments include: Without raising: "land" < "crooked" < "in it" < With raising: "melodious" < "around" < "fingernail, toenail" < "navel" <
Additionally, and *e were also raised to i when followed by a nasal, a voiced stop, and then either *e or a word-final *a followed by a nasal, despite those vowels not triggering i-affection. "butter" < "he/she steps (conjunct)" < <
Rounding of vowels by labiovelars In Primitive Irish, *a and *i were rounded to o and u respectively when preceded by Celtic labiovelars and or a consonant cluster containing them. The rounding of *i also required the following consonant to be palatalised. This rounding occurred after i-affection as "prays" (< ) faced rounding even though the rounded vowel was originally an *e. Since "buys" (< ) faced no rounding even though its stressed vowel was originally an *i, the rounding may also have taken place after a-affection as well, but Schrijver does not find the evidence for that to be reliable.
Examples of this rounding process include: "wounds, kills" < "pious" < "cauldron" < "worm" < "of a tree" < (the nominative singular is secondary) "portion" <
Original *a preceded by a labiovelar consonant and followed by *n and an originally voiceless stop was rounded and then broken into Old Irish . "was wounded" < "fifty" <
Compensatory lengthening before fricatives After a-affection occurred in Primitive Irish, dental and velar fricatives were dropped when immediately preceding a sonorant consonant, but transformed the preceding vowel into a long vowel or a diphthong. This development affected both stressed and unstressed syllables.