Verba (Conspectus) · sum · possum

A Latin verb is inflected to express five categories simultaneously, all marked in a single word-form. This concentration of grammatical information in one word is one of Latin's most distinctive features and what makes Latin verb-forms so dense:

(1) Person (persōna) — 1st (I/we), 2nd (you/y'all), 3rd (he/she/it/they). The personal ending of the verb specifies which.

(2) Number (numerus) — singular or plural. Combined with person: 1sg, 2sg, 3sg, 1pl, 2pl, 3pl — 6 person-number combinations.

(3) Tense (tempus) — six tenses (see § 154 below): present, imperfect, future, perfect, pluperfect, future-perfect.

(4) Mood (modus) — four moods (see § 155): indicative (statement of fact), subjunctive (will, possibility, contingency), imperative (command), infinitive (verbal noun).

(5) Voice (vōx) — active (subject does the action) or passive (subject receives the action). Some verbs are deponent ("passive in form, active in meaning" — see Lectiō XIX).

The verb's inflection is therefore far richer than the noun's. Consider: amō "I love" carries:
• Person: 1st
• Number: singular
• Tense: present
• Mood: indicative
• Voice: active
— five pieces of information packed into three letters! The Latin verb is, morphologically, the most information-dense single word in the language.

By contrast, English distributes the same information across separate words ("I love" — pronoun + verb) or even auxiliary constructions ("I will be loving" for future-active-progressive). Latin's compact morphology is what allows its flexible word-order: because each verb-form is morphologically self-identifying, it can be placed anywhere in the sentence without ambiguity.

The six Latin tenses split into two systems based on aspect (whether the action is incomplete/in-progress vs. completed):

Present-system (incomplete aspect, formed from the present stem):
• Present (amō): "I love / am loving" — current action.
• Imperfect (amābam): "I was loving / used to love" — past in-progress or habitual.
• Future (amābō): "I shall love / will be loving" — future incomplete.

Perfect-system (completed aspect, formed from the perfect stem):
• Perfect (amāvī): "I loved / have loved" — completed action; the most flexible Latin tense, covering both English simple past and present perfect.
• Pluperfect (amāveram): "I had loved" — completed before another past time.
• Future-Perfect (amāverō): "I shall have loved" — completed before a future time.

The same threefold contrast — present, past, future — recurs in each system, but the perfect system views the action as completed (the doer is now in a state resulting from the action). The Latin perfect's dual nature (event-perfect vs. state-perfect) is central; the English distinction between "did" and "have done" is collapsed in Latin into the single form fēcī.

Each tense exists in active and passive voices (apart from the few intransitive verbs that lack passive). And each tense has indicative and (where appropriate) subjunctive forms, plus appropriate non-finite forms (infinitives, participles).

Total combinations: 6 tenses × 2 voices × 2-3 moods + non-finite = approximately 100+ distinct forms per verb. Mastering this system is the central challenge of Latin learning.

The mood (modus) indicates how the speaker views the action — as fact, command, possibility, or simply named. Latin has four moods:

(1) Indicative (indicātīvus) — states a fact or asks a fact-question. The "default" mood: amat "he loves" (statement); amatne? "does he love?" (question). Used for assertion of reality. All six tenses have indicative forms.

(2) Subjunctive (coniūnctīvus) — expresses what is not asserted as fact: wish, possibility, command, condition, indirect statement, etc. amet "let him love / may he love". Has only four tenses (no future or future-perfect): present, imperfect, perfect, pluperfect. Treated extensively in Lectiō XXX.

(3) Imperative (imperātīvus) — issues a direct command. amā! "love!"; amāte! "love (you all)!". Limited to 2nd person (sg./pl.) in present. A "future imperative" (amātō) survives in formal/legal contexts.

(4) Infinitive (īnfīnītīvus) — names the action without person/number (verbal noun). amāre "to love". Six infinitives total (3 tenses × 2 voices). Treated in Lectiō XVIII.

To these four moods are added the verbal nouns and adjectives:
• participium (participle) — verbal adjective, 4 types.
• gerundium (gerund) — verbal noun in oblique cases.
• gerundīvum (gerundive) — passive future participle, with obligation sense.
• supīnum (supine) — verbal noun in 4th declension (acc./abl.).

The boundary between the moods and the non-finite forms is sometimes blurry. The infinitive, classed as a "mood" by traditional grammar, is really a verbal noun. The participles, gerund, and supine are non-finite forms that supplement the finite verb-system.

Every Latin verb is learned by its four principal parts:

(1) Present indicative active 1st sg. — amō "I love". Identifies the verb and gives the present stem.
(2) Present infinitive active — amāre "to love". Gives the conjugation (the long vowel reveals which conjugation).
(3) Perfect indicative active 1st sg. — amāvī "I (have) loved". Gives the perfect stem.
(4) Supine — amātum. Gives the participial stem from which perfect passive participle, future active participle, future passive infinitive, etc., are formed.

From these four forms the entire system of the verb can be derived. For irregular and "third-conjugation" verbs, these must be memorized; regular verbs follow predictable patterns.

The principal parts are the dictionary form of every Latin verb. When you look up amō, you find: amō, amāre, amāvī, amātum. These four are the key to all 100+ forms of the verb.

Three derivational rules connect the principal parts:

• Present stem: drop -ō from PP1 (or -ī from a deponent's PP1) → am-. Then add stem-vowel: amā-, monē-, rege-/regi-, capi-, audī-.
• Perfect stem: drop -ī from PP3 → amāv-, monu-, rēx-, cēp-, audīv-.
• Participial stem: drop -um from PP4 → amāt-, monit-, rēct-, capt-, audīt-.

From these three stems plus the appropriate endings (active, passive, indicative, subjunctive, etc.), every verb-form is generated. The "work" of learning a verb is the work of memorizing its four principal parts.

The verb sum "to be" is the most fundamental verb in Latin, used in every page of every author. It serves as:

• The main verb of "to be" sentences: Caesar dux est "Caesar is leader".
• The auxiliary in compound (periphrastic) tenses: perfect passive (amātus est "he was loved"), future passive, etc.
• The connecting verb for predicate nouns and adjectives: vir bonus est "the man is good".

Principal parts: sum, esse, fuī, futūrus. Note: sum is intransitive and has no passive voice; the supine slot is filled by futūrus, the future participle (active), which is a peculiarity.

The verb is athematic — meaning the personal endings attach directly to the root without a connecting vowel. This makes it irregular by Latin standards but normal by Indo-European standards (Greek eimi, ei, esti follows the same pattern).

Highlights of sum's irregularity:
• Present 1sg in -um (not -ō).
• Present 2sg, 3sg, 2pl with no theme vowel: es, est, estis.
• Imperfect with stem er- (from a different root): eram, erās, erat.
• Future with stem er-: erō, eris, erit.
• Perfect with stem fu- (yet another root): fuī, fuistī, fuit.
• Participle and infinitive: esse (inf.), fore (rare alt. fut. inf.), futūrus (fut. ptcp.).

Despite irregularity, the conjugation must be memorized perfectly — without it, no Latin sentence can be parsed.

possum "be able, can" — combination of pot- ("powerful, able") + sum. The conjugation is mostly sum's, with pot- prefixed. Phonetic rule: before s- (the bare stem of sum), pot- assimilates to pos-: pos-sum, pos-sumus; before vowels, pot- stands: pot-est, pot-erat, pot-erunt.

Principal parts: possum, posse, potuī. No passive voice (it's about ability, not suffering). No imperative. No participle (except poetic potēns, used as adjective: "powerful").

The verb governs an infinitive complement: possum venīre "I can come"; nōn possum dormīre "I cannot sleep"; poterat fugere "he was able to flee".

Possum is among the most frequent verbs in Latin, ubiquitous in classical prose for modal expressions. Its compound nature is transparent in some forms (pot-est, pot-erat) but obscured by assimilation in others (possum, possumus). The infinitive posse is unique — a peculiar single-word that you simply must memorize.

Compounds: rare, mostly impotens "powerless" (= adj. of impotēns, -entis) — used as adjective.

The verb sum forms compounds with prepositional prefixes. All conjugate exactly like sum, simply with the prefix attached. The meanings extend the basic "be" with directional or relational sense:

• absum, abesse, āfuī, āfutūrus "be away, be absent" — ab + sum. diū āfuit "he was absent for a long time".
• adsum, adesse, adfuī, adfutūrus "be present, be at hand, support" — ad + sum. adsum tibi "I am present to you = I support you".
• dēsum, dēesse, dēfuī "be lacking, fail" — dē + sum. dēest mihi auxilium "I lack help".
• īnsum, inesse, īnfuī "be in, be contained in" — in + sum. inest virtūs "virtue is within (someone)".
• intersum, interesse, interfuī "be among, take part in, concern" — inter + sum. magnopere interest "it greatly concerns".
• obsum, obesse, obfuī "be against, hinder, harm" — ob + sum. obest mihi "it is against me".
• praesum, praeesse, praefuī "be in charge of, command" — prae + sum. exercituī praefuit "he commanded the army".
• prōsum, prōdesse, prōfuī, prōfutūrus "be of use, benefit" — prō + sum. Note: -d- inserts before vowels (prōdes, prōdest, prōdesse).
• subsum, subesse, subfuī "be under, be at hand" — sub + sum.
• supersum, superesse, superfuī "be left over, survive" — super + sum. nēmō supererat "no one was left".

The -d- insertion in prōsum is a phonological remnant: between two vowels, an old d intervenes (prō-d-est) but vanishes before consonants (prōsum, prōsumus).

The compounds of sum often govern dative (compound preposition's natural object): absum tibi, adsum tibi, prōsum tibi, obsum tibi — all "to you / for you / against you" with the dative.

The same set of personal markers attaches to all four conjugations. Once learned, this universal pattern unlocks all regular verbs:

Active personal endings:
• 1sg: -ō / -m (depending on tense)
• 2sg: -s
• 3sg: -t
• 1pl: -mus
• 2pl: -tis
• 3pl: -nt

Passive personal endings:
• 1sg: -or / -r
• 2sg: -ris / -re (alternating; both classical)
• 3sg: -tur
• 1pl: -mur
• 2pl: -minī
• 3pl: -ntur

Perfect-system active endings (unique — different from present-system):
• 1sg: -ī
• 2sg: -istī
• 3sg: -it
• 1pl: -imus
• 2pl: -istis
• 3pl: -ērunt / -ēre

Imperative endings:
• 2sg: bare stem (amā, monē, rege, audī).
• 2pl: -te attached to stem (amāte, monēte, regite, audīte).
• Future imperatives: -tō, -tōte, -ntō (rare in classical prose, common in legal/formal texts).

Tense-mood markers attach between the stem and the personal ending:
• Imperfect indicative: -bā- (1·2 conj.) or -ēbā- (3·4 conj.).
• Future indicative: -bō, -bi- (1·2 conj.) or -a-/-ē- (3·4 conj.).
• Perfect: stem-vowel + -v- or other perfect formations.
• Pluperfect: -erā- (perfect stem + auxiliary endings).
• Future-perfect: -eri-.
• Present subjunctive: -e- (1 conj.) or -ā- (2·3·4 conj.).
• Imperfect subjunctive: present infinitive + endings.
• Perfect subjunctive: -eri-.
• Pluperfect subjunctive: -issē-.

This combinatorial system means that learning one regular verb thoroughly (typically amō) gives mastery of about 80% of all Latin verbs. The principal parts and the ending tables are the keys; everything else is application.