Post-war structuralist phonology greatly emphasized phonemics and largely ignored morphophonemics. But in 1959, Morris Halle’s Sound Pattern of Russian argued that the distinction between allophony and alternation has little cognitive importance, and in fact the distinction leads to an unnecessary duplication of effort. As a result of Halle’s forceful arguments, the contrast between phonemic and morphophonemic processes plays little role in modern phonological theory. I would like to go one step further and suggest that patterns of alternation are actually more principled facts than those of allophony. Simply put, a speaker must command the pattern of alternation in their language; but it is not at all clear whether they exploit allophony when constructing their lexical entries. This is highlighted most clearly by the notions of lexicon optimization, Stampean occultation, and richness of the base in Optimality Theory, though as Hale et al. (1998) note, similar points apply to rule-based theories.

In writing the Romans did not draw distinctions between the high monophthongs [i, u, iː, uː] and glides [j, w], respectively. This naturally led structuralist linguists (e.g., Hall 1946) to suggest that the glides are allophones of the high monophthongs. There are some apparent problems with this suggestion, though not all of them are fatal. One point that has largely been ignored in this discussion is that Classical Latin has at least four types of plausible alternations between high monophthongs and the corresponding glides. In this squib I review these alternations.

Deverbal -u- derivatives

There are a large number of adjectival derivatives formed from verbal stems by the addition of -u- and the appropriate agreement suffixes, e.g., masculine nominative singular (masc. nom.sg.) -u-us, feminine nom.sg. -u-a, and neuter nom.sg. -u-um, and so on. These derivatives have a similar semantics to past participles (“having been Xed”) but in some cases have a secondary meaning “able to be Xed”. For example, the masc. nom.sg. form dīuiduus [diːwi.du.us] means ‘divided’ (cf. dīuidō [diːwi.doː] ‘I divide’) but also ‘divisible’. This is a fairly productive process, as the following examples show. (I have taken the liberty of leaving off certain further productive derivatives, such as intensified adjectives in per-.)

(1) assiduus ‘constant, ambiguus ‘hither and thither’, annuus ‘annual, arduus ‘elevated’, cernuus ‘bowed forward’, circumfluus ‘flowing around’ (refluus ‘ebbing’), cōnspicuus ‘visible’, contiguus ‘neighboring’, continuus ‘continuous’, dīuiduus ‘divided; divisible’ (indīuiduus ‘undivided; indivisible’), exiguus ‘strict’, fatuus ‘foolish’, incaeduus ‘uncut’,  ingenuus ‘indigenous’, irriguus ‘irrigated’, mēnstruus ‘monthly’, mortuus ‘dead’ (dēmortuus ‘departed’, intermortuus ‘decayed’, praemortuus ‘prematurely dead’), mūtuus ‘borrowed’ (prōmūtuus ‘paid in advance’), nocuus ‘harmful’ (innocuus ‘harmless’), occiduus ‘westerly’, pāscuus ‘for pasturing’, perpetuus ‘perpetual’, perspicuus ‘transparent’, praecipuus ‘particular’, prōmiscuus ‘indiscriminate’, residuus ‘remaining’,  riguus ‘irrigated’, strēnuus ‘brisk’, succiduus ‘sinking’, superuacuus ‘superfluous’, uacuus ’empty’, uiduus ‘destitute’

In all the above cases …uus is read [u.us]. However, when the stem ends in a liquid [l, r] …uus is read [wus], indicating that the deadjectival affix is realized as [w].

(2)
a. caluus ‘bald’, fuluus ‘reddish-yellow, tawny’, giluus ‘pale yellow’, heluus ‘honey yellow’
b. aruus ‘arable’, curuus ‘bent’ (incuruus ‘bent’), furuus ‘dark, swarthy’, paruus ‘small’, prōteruus ‘violent’, toruus ‘savage’

It is interesting to note that the contexts where -u- is realized as [w] align with a well-known allophonic generalization (Devine & Stephens 1977: 61., 134f.): a u preceded by a (tautomorphemic) coda liquid or front glide, and followed by a vowel, is realized as [w], as in silua [sil.wa] ‘forest’ or ceruus [ker.wus] ‘deer’, but is realized as a vowel when the preceding consonant is either a nasal, an obstruent, or part of a consonant cluster, as in lituus [li.tu.us] ‘trumpet’ or patruus [pa.tru.us] ‘paternal uncle’.

Two residual issues remain. First, when the verbal stem end in qu [kw], the adjectival derivative is spelled …quus. By the normal rules of spelling this would be read as [kwus], which would suggest that a zero allomorph of the adjectival suffix is selected for here.

(3) aequus ‘equal’, antīquus ‘old’, fallāciloquus ‘falsely speaking’ (fātiloquus ‘prophetic’, flexiloquus ‘ambiguous’, grandiloquus ‘grandiloquent’, magniloquus ‘boastful’, uāniloquus ‘lying’, uersūtiloquus ‘slyly speaking’), inīquus ‘unjust’, longinquus ‘distant’, oblīquus ‘slanting, oblique’, pedisequus ‘following on foot’, propinquus ‘near’, reliquus ‘remaining’

This is consistent with the metrical evidence. For instance in the following verse, aequus must be read as bisyllabic.

(4)
hoc opus hic labor est paucī quōs aequus amāuit (Verg., Aen. 6.129)[ok.ko.pu|sik.la.bo|rest.paw|kiː.kwoː|saj.kwu.sa|maːwit]

Secondly, there are a number of deverbal derivatives in -u-us where the verb form also has a stem-final [w]. In this case we also observe [wus].

(5)
a. cauus [ka.wus] ‘hollowed; hollow’ (concauus ‘hollow’); cf. cauō [ka.woː] ‘I excavate’
b. flāuus [flaː.wus] ‘yellow, gold, blonde’ (sufflāuus ‘yellowish’); cf. flāueō [flaː.we.oː] ‘I am yellow’
c. (g)nāuus [naː.wus] ‘active’ (īgnāuus ‘lazy’); cf. nāuō [naː.woː] ‘I do s.t. enthusiastically’
d. nouus [no.wus] ‘new’; cf. nouō [no.woː] ‘I renew’
e. saluus [sal.wus] ‘safe; well’; cf. salueō [sal.we.oː] ‘I am well’
f. uīuus [wːi.wus] ‘living’ (rediuīuus ‘restored to life’); cf. uīuō [wiː.woː] ‘I live’

This may be another context where the adjectival suffix has a zero allomorph, though it is not clear whether we are looking at the same derivational process as above.

The foregoing discussion leads me to posit a deverbal adjective-forming suffix /-u-/ with two phonologically-predictable allomorphs: [w] before liquids, and zero before [kw] and possibly, [w].

The “third stem”

Schoolchildren learning Latin memorize four forms (or principal parts) of each verb: the first person singular (1sg.) present active indicative (e.g., amō ‘I love’), the present infinitive (amāre ‘to love’), the 1sg. perfect active (amāvī ‘I loved’), and the perfect passive participle (amātus masc. nom.sg. ‘loved). The first two principal parts effectively index the so-called “present stem” of the verb, and the third principal part gives the so-called “perfect stem”. The relationship between the present and perfect stem is often unpredictable. Some perfect stems lengthen a monophthong in the final syllable of the present stem (e.g., legō/lēgī ‘I choose/chose’); some perfect stems omit a post-vocalic nasal in the final syllablem with comcomitant lengthening (uincō/uīcī ‘I win/won’); some are mutated by the addition of a -s- perfect suffix (dīcō/dīxī [diː.koː, diːk.siː] ‘I say/said’); others bear a CV-reduplication prefix, and so on. This has lead some to suggest that the latter two stems are essentially “listed” or “stored” for all verbs. This is, for instance, the position of Lieber (1980:141f., 152f.), but has been disputed by Aronoff (1994: chap. 2) and Steriade (2012), among others, who claim there are many productive regularities in both cases.

The majority of verbs have perfects that consist of the bare verb root, the theme vowel, a high back vocoid perfect suffix, and the appropriate person-number agreement suffixes (e.g., 1sg. -ī-). The perfect suffix is preceded by a theme vowel and as the appropriate agreement suffixes are all vowel-initial, it is always intervocalic. Allophonically, this is a context where [u] is never found but [w] is, and this is what we find here: amāuī [a.maː.wiː] ‘I loved’. This type of perfect is in fact found in all conjugations, and found in the overwhelming majority of 1st (-ā- theme vowel) and 4th conjugation (-ī-) verbs (Aronoff 1994:43f.).

(6)
a. cōnsōlāuī [kon.soː.laː.wiː], portāuī [por.taː.wiː] ‘I carried’
b. dēlēuī [deː.leː.wiː] ‘I destroyed’, plēuī [pleː.wiː] ‘I filled up’
c. cupīuī [ku.piː.wiː] ‘I desired’, petīuī [pe.tiː.wiː] ‘I sought’
d. audīuī [aw.diː.wiː] ‘I listened to’, mūnīuī [muː.niː.wiː] ‘I fortified’

However, there is an alternative formulation in which the theme vowel is omitted,  placing the perfect suffix to the right of a consonant, and in this context it is instead realized as [u]. This type of perfect is also found in all conjugations but is most common in the 2nd (-ē-) conjugation.

(7)
a. domuī [do.mu.iː] ‘I tamed’, uetuī [we.tu.iː] ‘I forbid’
b. docuī [do.ku.iː] ‘I taught’, tenuī [te.nu.iː] ‘I held’
c. rapuī [rap.u.iː] ‘I snatched’, texuī [tek.su.iː] ‘I wove’
d. aperuī [a.pe.ru.iː] ‘I opened’, saluī [sa.lu.iː] ‘I leapt’

Together the patterns in (6-7) account for the vast majority of perfects in all conjugations except the 3rd (itself a grab-bag of etymologically dissimilar verbs).

I propose that the default perfect suffix is /-u-/ and that it undergoes glide formation to [w] in (6), in intervocalic position, a generalization consistent with the allophonic facts. In (7), when adjacent to the verb root, glide formation is blocked. However, the examples in (7) cannot take a “free ride” on any allophonic generalization. As can be seen in (7d), the perfect suffix does not form [l.w, r.w] syllable contact clusters, unlike the adjectival suffix in (5). There is a surfeit of possible analyses for the failure of glide formation in this context: it might be an effect specific to the perfect suffix or to the category of verb, or the result of cyclicity or phase-based spellout. We leave the question open for now.

The “fourth stem”

The form of the perfect passive participle, the fourth principal part, similarly problematic. For many verbs, the perfect passive participle is formed by adding to the verb root a -t- suffix and the appropriate agreement suffixes (e.g., in citation form, the masc. nom.sg. -us), once again sometimes accompanied by lengthening of the stem-final vowel and/or leftward voice assimilation (an exception-less rule of Latin) triggered by the -t- as in (8b).

(8)
a. docuī [do.ku.iː] ‘I teach’, doctus [dok.tus] masc. nom.sg ‘taught’
b. tegō [te.goː] ‘I clothe’, tēctus [tek.tus] masc. nom.sg. ‘clothed’

Two verb roots which end in consonant followed by a high back vocoid and form a -t- perfect passive participle: soluō [solwoː] ‘I loosen; I explain’ and uoluō [wolwoː] ‘I roll’. This places the root-final high back vocoid, by hypothesis /u/, between two consonants, a context where glides are forbidden. The result is solūtus [soluːtus] and uolūtus [woluːtus]. However, it should be noted that this particular pattern is limited to these two verbs and their derivatives, and that the long ū is unexpected unless it reflects stem vowel lengthening (cf. tēctus above).

Synizesis and diaeresis

Latin poetry exhibits variation in glide formation. (The following examples are all drawn from Lehmann 2005). Synizesis, the unexpected overapplication of glide formation in response to the meter, can be seen in the following verse.

(9)
tenuis ubī argilla et dūmōsīs calculus aruīs (Verg., G. 2.180)
[ten.wi.su|biːr.gil|let.duː|mōsīs|kal.ku.lu|sar.wiːs]

In this verse, tenuis ‘thin’ occurs initially, which requires that the first syllable be heavy. The only way to accomplish this is to read it as the bisyllabic [ten.wis] rather than the expected trisyllabic [te.nu.is]. Similarly, in another verse (Verg., Aen. 8.599), abiēte, the ablative singular of abiēs ‘silver fir’, must be read as trisyllabic [ab.jeː.te] rather than the expected [ab.i.eː.te].

On the other hand, the poets also make use of diaeresis, or apparent underapplication of glide formation. For example, siluae, the genitive singular of silua ‘forest’, is in one verse (Hor., Carm. 1.23.4) read as trisyllabic [si.lu.aj] rather than as the expected bisyllabic [sil.waj]. The conditions governing synizesis and diaeresis are not yet well understood, but they constitute further evidence for the close grammatical relationship between [i ~ j] and [u ~ w] in Classical Latin.

Conclusion

We have seen four ways in which the Latin high vocoids alternate between vowels and glides. Together, these four patterns provide indirect evidence for the hypothesis that Latin glides are allophones of the corresponding high vowels, though there are some minor dissociations between patterns of allophony and alternations.

[Earlier writing about Latin glides: Latin glides and the case of “belua”]

References

Aronoff, Mark. 1994. Morphology by itself: stems and inflectional classes. Cambridge: MIT Press.
Devine, Andrew M., and Stephens, Laurence D. 1977. Two studies in Latin phonology. Saratoga: Anma Libri.
Hall, Robert A. 1946. Classical Latin noun inflection. Classical Philology 41(2): 84-90.
Hale, Mark and Kissock, Madelyn, and Reiss, Charles. 1998. Output-output correspondence in Optimality Theory. In Proceedings of WCCFL, pages 223-236.
Halle, Morris. 1959. The sound pattern of Russian. The Hague: Mouton.
Lehmann, Christian. 2005. La structure de la syllabe latine. In Touratier, Christian (ed.), Essais de phonologie latine, pages 157-206. Aix-en-Provence: Publications de l’Université de Provence.
Lieber, Rochelle. 1980. On the organization of the lexicon. Doctoral dissertation, MIT.
Steriade, Donca. 2012. The cycle without containment: Latin perfect stems. Ms., MIT.