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.

• 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.
• Where u-infection occurs in the stressed syllable, stressed 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 preceding the stem-final consonant(s), /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 become /ə/ and unstressed non-absolute-final u-infected diphthongs become /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/