Conjugation: The Verb System
Latin verbs are sorted into four regular conjugations by the vowel that sits in front of -re in the present infinitive: amā-re, monē-re, reg-ere, audī-re. That vowel decides every ending the verb will ever take.
Each verb advertises its full grammatical address through four principal parts: amō, amāre, amāvī, amātum.
Those four words unlock all six tenses, three moods, and two voices — present, perfect, and supine stems each generate their own family of forms. Memorize the principal parts of a verb and you have memorized the verb.
On top of the four regulars sit the deponents (passive form, active meaning — sequor "I follow"), the irregulars (sum, possum, ferō, eō, volō, fīō), and a handful of defectives. This page is the orientation map; the spokes hold the full paradigms.
Learnings0 core · 1 AP claim
AP framework claims (1)— verbatim from AP CED
The vowel before -re in the infinitive identifies the conjugation; the four principal parts unlock every form.
3rd and 3rd-iō share the same -ere infinitive — the 1st sg in -iō is the giveaway that you are in the 3rd-iō subgroup.
| Case | Conjugation | Model verb | 1st sg. pres. | Infinitive | Stem vowel |
|---|---|---|---|---|---|
| 1st | amō, amāre, amāvī, amātum (love) | amō | amāre | ā | |
| 2nd | moneō, monēre, monuī, monitum (warn) | moneō | monēre | ē | |
| 3rd | tegō, tegere, tēxī, tēctum (cover) | tegō | tegere | ĕ | |
| 3rd-iō | capiō, capere, cēpī, captum (seize) | capiō | capere | ĕ + i | |
| 4th | audiō, audīre, audīvī, audītum (hear) | audiō | audīre | ī |
See It In Action
— Verg. Aen. i. 1
Canō is a 3rd-conjugation verb (infinitive canere); the -ō ending is the same personal ending the 1st (amō) and 4th (audiō) use. The conjugation lives in the stem, not the ending.
— B. G. i. 1
Est divisa is a perfect-passive periphrasis: the irregular verb sum plus the supine-stem participle divisa together form one perfect tense — a preview of how the third (supine) stem powers the whole passive perfect system.
— Verg. Aen. i. 229
Adloquitur looks passive — -tur is the 3rd sg. passive ending — but it is a deponent. Venus does the speaking; the form just inherits passive morphology with no passive meaning.
— Verg. Aen. iii. 715
Two conjugations side by side: monstrante is 1st-conjugation present participle (-ante), secutus is 3rd-conjugation deponent perfect participle. Same line, different stems, different families.
Both conjugations use the -ere infinitive. The 1st sg form (and a handful of present-system endings) is the only reliable tell.
1st sg in -ō, infinitive in -ere
tegō, tegere
I cover, to cover
1st sg in -iō, infinitive in -ere
capiō, capere
I seize, to seize
Tip: Look at the first principal part. If it ends in -iō with a short -ere infinitive, you are in 3rd-iō (capiō, faciō, iaciō, fugiō, cupiō). The i will reappear in 3pl pres. (capiunt) and elsewhere.
You meet capiunt in a Latin sentence. The 1st principal part is capiō, infinitive capere. Which conjugation is capiō, and why?
Study Tips
- •Drill the principal parts out loud — amō, amāre, amāvī, amātum. The four-word rhythm is how every Latinist actually stores verbs in memory.
- •Identify the conjugation by the second principal part (the infinitive), not the first. capiō looks 4th but its infinitive capere shows it is 3rd-iō.
- •When a verb feels passive but the dictionary lists no active form (sequor, hortor, loquor), you have a deponent. Translate it actively.
- •Keep the three stems straight — present, perfect, supine. If you know which stem a form is built on, you have already narrowed the tense to two or three options.