What are the rules of forming past participle tense and perfect tense of a verb in Latin?

For example, about the word "parsimony (n.)", from etymonline

early 15c., from Latin parsimonia "sparingness, frugality, thrift," from pars-, past participle stem of parsi, perfect tense of parcere "to spare, save, refrain from, use moderately" (which is said to be unrelated to Latin parvus "small," parum "too little") + -monia, suffix signifying action, state, or condition.

  • Past participle is not a tense; it's a root verb form. Perfect tense is a separate root verb form. Traditionally, one learns four "principal parts" of a Latin verb, from which one can construct all the other verb forms. There are several possibilities, exceptions, and idioms, so that, in essence, one must know: (1) the first person singular present active indicative form (2) the infinitive (3) the 1s perfect form and (4) the perfect passive participle. E.g, videō, vidēre, vīdī, vīsus , respectively, 'I see, to see, I saw, seen'.
    – jlawler
    Oct 23 '13 at 2:26
  • Every verb has their own collection of parts, and there are lots of rules. And exceptions. In the end, you just learn the forms.
    – jlawler
    Oct 23 '13 at 2:28
  • @jlawler: Thanks! What are some general rules then?
    – Tim
    Oct 23 '13 at 2:54
  • Here's a starter set.
    – jlawler
    Oct 23 '13 at 15:27

There is no real way to predict the perfect stem or the supine stem (past-participle stem) of a Latin verb; there are only probabilities. One normally learns the past stems of a verb along with its present stem and conjugation group if they are irregular.

The regular suffix to form the perfect stem is by adding -v- to the present stem, so after the theme vowel. This is very common, especially for verbs of the -a- conjugation, and also somewhat common for the -i- conjugation.

voca-re → voca-v-i

audi-re → audi-v-i

quaer-ĕ-re / quaes-ĕ-re → quaes-i-v-i or quaes-i-i (r changes into s)

Another common way of forming the perfect stem is by removing the theme vowel (if present) and adding -u-. This is especially common for verbs of the -ē- conjugation, but by no means limited to it.

terrē-re → terr-u-i

evanesc-ĕ-re → evan-u-i (ingressive present suffix -sc- disappears)

Adding /s/ is also quite frequent, especially with consonant stems. The resulting letter may be an x if the present stem ended on -c- or -g-.

mitt-ĕ-re → mis-i

teg-ĕ-re → tex-i

torquē-re → torsi

Many verbs do not get a suffix at all, especially but not exclusively with consonant stems, but the vowel in the stem will be lengthened compensatorily, and sometimes changed qualitatively:

vĕni-re → vēn-i

vĭdē-re → vīd-i

vinc-ĕ-re → vīc-i (nasal present infix disappears)

fund-ĕ-re → fūd-i (nasal present infix disappears)

ăg-ĕ-re → ēg-i (vowel changes)

făc-ĕ-re → fēc-i (vowel changes)

Many verbs of the -i- conjugation have both -v-i and -i:

audi-re → audi-i / audi-v-i

i-re → i-i / ī-v-i

Some verbs undergo reduplication, which is an artefact from proto- or pre-Latin, if I remember correctly. This, too, is most common with consonant stems. The vowel will often change in length and quality.

fall-ĕ-re → fe-fell-i (vowel changes)

caed-ĕ-re → cĕ-cīd-i (vowel changes)

tang-ĕ-re → te-tig-i (nasal infix disappears; vowel changes)

făc-ĕ-re → archaic fe-fec-i (vowel changes)

păr-ĕ/i-re → pe-pĕr-i (vowel changes)

pell-ĕ-re → pĕ-pŭl-i (vowel changes)

posc-ĕ-re → po-posc-i (o-reduplication)

spondē-re → spo-pond-i (apparently unique, based on Proto-Indo-European perfect)

But none of these rules are remotely strict or consistently applied. And many verbs have several perfect stems that can be used interchangeably.

The supine stem (past participle) is regularly (but by no means always) formed by adding -t- after the theme vowel, if present, where theme vowel -ē- changes into -i-. This -i-tus sometimes also happens with consonant stems. Supine stems are just as irregular and unpredictable as perfect stems, and many verbs even have two interchangeable supine stems.

voca-re → voca-t-us

audi-re → audi-t-us

terrē-re → terr-i-t-us

pet-ĕ-re → pet-i-tus

cognosc-ĕ-re → cogn-i-t-us (ingressive suffix -sc- disappears)

quaer-ĕ-re → quaes-i-tus (r changes into s)

However, in many cases the suffix -t- has to come immediately after a consonant; in that case, many things can happen. This is perhaps unexpectedly not limited to consonant stems.

After p and c, it can come immediately after:

cap-ĕ-re → cap-t-us

fac-ĕ-re → fac-t-us

The dental consonant -t- plus -t- often but not always becomes -ss-. This sometimes also happens after -d-.

mitt-ĕ-re → mis-s-us

ced-ĕ-re → ces-s-us

But -d- plus -t- usually becomes -s-.

fund-ĕ-re → fus-us (nasal present infix disappears)

caed-ĕ-re → caes-us

accend-ĕ-re → accens-us

spondē-re → spons-us

After -l-, it is turned into -s-.

fall-ĕ-re → fal-s-us

pell-ĕ-re → pul-s-us (vowel changes)

Consonant g becomes unvoiced:

ag-ĕ-re → ac-t-us

frang-ĕ-re → frac-t-us (nasal infix disappears)

Consonant b becomes unvoiced and t may or may not turn into s (but verb stems on -b- are rare at any rate):

lab-i (deponens) → lap-s-us

scrib-ĕ-re → scrip-t-us

  • Aside from one-off irregulars like ferre, there are basically four processes to form the perfect stem; each one comes from a different I-E tense formation: The regular -V (thematic or athematic), the sigmatic aorist -S, the reduplicative perfect, and vowel lengthening. The verb categories for forming the perfect stem crosscut the traditional conjugations, which are just the verb categories for forming the present stem. It makes a wonderful linguistics problem, and I used to put it on my Intro Ling exams.
    – jlawler
    May 17 '18 at 2:14
  • 1
    @jlawler: Quite so, but there are still conexions between conjugation and perfect stem. E.g. -v- strongly correlates with -a- conjugations, and -u- with -e- conjugations, as mentioned.
    – Cerberus
    May 17 '18 at 12:18

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