Old Irish/Morphology

Short Monophthong Alternations in Nominal Stems

Due to various prehistoric developments in Goidelic phonology and morphology, the stressed vowel (i.e. the vowel in the initial syllable), if it is a short monophthong, can undergo alteration. Depending on the quality of the vowel and the paradigmatic form, it can either be raised or lowered. It can also diphthongise by way of u-infection in a limited number of paradigmatic forms. If the stem consists of multiple syllables, then the root vowel isn't affected by u-infection; rather, the unstressed vowel /ə/ preceding the stem-final consonant(s) is replaced by /u/. Outlined below are the processes behind these alternations, and then for each declension class are outlined the exact set of rules for the appropriate alternations within the paradigm.

When following these rules, an important point to consider is the historical form of the root vowel itself which serves as a point of reference. While the observable effects of raising and lowering the root vowel appear to be the reverse of each other, the fact that there are more restrictions applied to raising means that they should be treated as separated processes with differing results. The reference root vowel in a stem can either experience raising or lowering, but not both. In masculine o-stems, a useful reference point is the voc. sg. which neither gets raised nor lowered. While it's often traditional to take the nom. sg. as the reference point, doing so will only serve to mislead, causing the perception that rules regarding the blocking of raising are being violated.

Another important point to consider is the implementation of nouns borrowed from other languages (such as Latin) which have not undergone the previous sound changes in the chronological developments. Rather, these forms are implemented into the morphology by way of analogy, thus the resulting effects can also appear to violate certain rules, but that is only because the rules never applied to these forms during the prehistoric development of Goidelic. A number of other Celtic forms also experience raising contradictory to rules regarding their historical root vowel. These developments could be explained by internal analogous development. Whatever the case, it is best to consider raising or lowering as a one-way process once one has determined the reference point.

• Where the root vowel contains the stress, if it is a short monophthong, it can undergo raising or lowering.
  • Where raising occurs, e raises to i and o raises to u.
    • Raising is blocked if the vowel is followed by a voiceless consonant.
    • Raising is blocked if the vowel is followed by a consonant cluster, other than a nasal + plosive cluster.
  • Where lowering occurs, i lowers to e and u lowers to o.
    • Lowering of i to e was historically blocked by -nd in find.
• The vowel preceding the stem-final consonant(s), whether it is stressed or unstressed, as long as it is a short monophthong, can undergo u-infection.
  • Where u-infection occurs in the stressed syllable, a, e, i and o diphthongise into au, eu, iu and ou respectively.
    • Historically geminated -ss- blocked u-infection of stressed e in mes.
    • Exceptionally, macc, salm and folt do not experience u-infection.
  • Where u-infection occurs in an unstressed syllable, /ə/ is replaced by /u/.

Masculine o-Stems

1. The voc. sg. contains the reference root vowel. It is neither raised nor lowered.
2. The gen. sg., prep. sg., nom. pl., acc. pl. and voc. pl. are all raised.
3. All other forms are lowered.
4. The prep. sg. is u-infected.
5. Only stressed a is u-infected in the acc. and voc. pl.

Neuter o-Stems

1. The gen. and prep. sg. are raised.
2. All other forms are lowered.
3. The prep. sg. is u-infected.

Chronological Background

Below is a list of the relevant developments in chronological order that help give context behind these vowel alternations in their final form.

1. Unstressed long vowels were shortened, unless they were followed by /h/.
2. Stressed interconsonantal /e, o/ raised to /i, u/ respectively when the following syllable consisted of a high monophthong: /i, iː, u, uː/.
   1. The following consonant must only be a voiced single consonant or a nasal + plosive cluster.
3. Stressed /a/ was diphthongised to /au̯/ when the vowel in the following syllable consisted of /u, uː/.
4. Stressed and unstressed /e, i, o/ were diphthongised to /eu̯, iu̯, ou̯/ respectively when the vowel in the following syllable consisted of /u/, but not /uː/.
   1. The geminated /sː/ in /esːu/ blocked this diphthongisation of stressed /e/ but allowed it for unstressed /e, i/.
5. Stressed and unstressed /i, u/ lowered to /e, o/ respectively when the following syllable consisted of non-high back monophthongs: /a, aː, o, oː/.
   1. The /n̪ːd/ in /in̪ːda/ blocked this lowering of /i/.
6. Final /h/ shifted to the following word or disappeared altogether.
7. Final short vowels disappeared (apocope).
8. Final long vowels shortened.
9. Unstressed non-absolute-final monophthongs underwent reduction in quality, becoming /ə/, and unstressed non-absolute-final u-infected diphthongs became /u/.

Examples

• nom. sg. ball /bal̪ː/ < /bal̪ːa/ < /bal̪ːah/
• prep. sg. baull /bau̯l̪ː/ < /bau̯l̪ːu/ < /bal̪ːu/ < /bal̪ːuː/
• acc. pl. baullu /bau̯l̪ːu/ < /bau̯l̪ːuː/ < /bau̯l̪ːuːh/ < /bal̪ːuːh/

• nom. sg. fer /ɸʲer/ < /wera/ < /werah/ < /wirah/
• voc. sg. fir /ɸʲirʲ/ < /wire/
• gen. sg. fir /ɸʲirʲ/ < /wiri/ < /wiriː/
• prep. sg. fiur /ɸʲiu̯r/ < /wiu̯ru/ < /wiru/ < /wiruː/
• acc. pl. firu /ɸʲiru/ < /wiruː/ < /wiruːh/