The Four Conjugations

Latin’s four conjugations are families of verbs that build the present system in similar ways. You identify the family principally from the present active infinitive: -āre for first conjugation, -ēre for second, short -ere for third, and -īre for fourth. The classification predicts many forms, but it does not predict a verb’s perfect or supine stem; that is why dictionaries give several principal parts.

The numbering is a grammatical label, not a ranking. A third-conjugation verb is not “more advanced” than a first-conjugation verb. It simply uses a different pattern of stem vowels and connecting vowels.

The diagnostic principal parts

The macron distinguishes second-conjugation -ēre from third-conjugation -ere. That vowel quantity is not decorative: monēre and regere belong to different productive patterns. In manuscripts and many printed editions macrons are absent, so the first principal part helps: second-conjugation verbs characteristically have -eō (moneō), whereas ordinary third-conjugation verbs have -ō (regō).

The matching mone- of monet and monēre signals the second conjugation. Quantity remains long in the infinitive even though pedagogical spelling may omit it outside this guide.

First conjugation: the stable ā

First-conjugation verbs have an ā-stem, most clearly visible in amāre, amāmus, and amātis. Before some endings the vowel is shortened or contracted: amō, not amāō, and amat, with a short vowel before final -t in Classical pronunciation.

The future vocābimus belongs to the first-conjugation -b- future pattern. Classification therefore predicts more than the present tense: it organizes the whole present system. See the dedicated tense pages for full paradigms.

Second conjugation: long ē

The second conjugation has a long ē in its present stem: monēre, monēs, monēmus. Do not confuse it with a third-conjugation spelling when macrons are absent.

Here maneō, manēre “remain” is second conjugation, while the adverb māne “in the morning” has a different vowel and grammatical identity. Macrons expose the distinction.

The present respondēs shows -ē-; the future intellegēmus happens to show -ē- too, but intellegō, intellegere is third conjugation. A single finite form may be ambiguous as a conjugation diagnostic. Principal parts settle the question.

Third conjugation: short e and changing connecting vowels

Third-conjugation infinitives end in short -ere. Their present indicative displays a series of connecting vowels: regō, regis, regit, regimus, regitis, regunt. The stem is best treated as reg-; the visible vowel before the ending varies.

Curritis and deponent sequimur follow third-conjugation present-system patterns, although sequor has passive-looking endings and active meaning. Deponent voice is a lexical property discussed separately.

Do not infer that dūcit comes from a second-conjugation infinitive merely because English “lead” has a long vowel. Its principal parts begin dūcō, dūcere; grammatical class is a Latin morphological fact.

Fourth conjugation: long ī

Fourth-conjugation verbs have -īre and preserve ī widely: audīs, audīmus, audītis. In the third-person plural present, a connecting u appears: audiunt.

This sentence contrasts fourth-conjugation audiunt with third-conjugation intellegunt. Both end in -unt, so work backward through the full form and confirm with principal parts.

The ī in aperīmus identifies the fourth-conjugation present pattern. The subjunctive intrent belongs to first-conjugation intrō, intrāre: similar meanings do not imply similar morphology.

The third-conjugation -iō subgroup

Verbs such as capiō, capere, cēpī, captum have a third-conjugation infinitive but an -iō first principal part. They are traditionally called third-conjugation -iō verbs or “mixed conjugation” verbs. They combine third-conjugation diagnostics with i in many forms: capiō, capis, capit, capimus, capitis, capiunt.

Capiēmus uses the -ē- future shared by third -iō and fourth conjugation, not the first/second-conjugation -b- future. Classifying capiō as fourth from its first-person singular would therefore produce wrong forms. The infinitive capere controls the classification.

What conjugation does—and does not—predict

Conjugation predicts the formation of present, imperfect, and future forms, along with the present subjunctive, present infinitive, present participle, and related present-stem forms. It does not reliably predict the perfect or supine stem.

The Principal Parts as a Predictive System page shows how those additional dictionary forms supply what conjugation alone cannot.

Some verbs are irregular enough not to fit neatly into the four regular conjugations: sum, esse “be,” possum, posse “be able,” and ferō, ferre “carry” are central examples. Others are defective, lacking forms that a full paradigm would predict. Such lexical exceptions are not evidence that conjugations are useless; they show why conjugation and principal parts work together.

A production decision

To form a present-system form, retrieve the infinitive and first principal part. Identify -āre, -ēre, -ere, or -īre. If it is -ere, check for -iō in the first principal part. Then use the appropriate tense/mood pattern and finally choose the person-number and voice ending. Do not begin with an English ending such as “-ed” or “will”: English packages time and aspect differently.

All three forms come from third-conjugation scrībō, scrībere. English uses an auxiliary for the future and progressive paraphrases elsewhere; Latin changes the finite form according to its own present-system architecture.

Common Mistakes

1. Ignoring vowel quantity in -ēre versus -ere

2. Classifying capiō as fourth conjugation

3. Predicting the perfect from the conjugation alone

4. Building from the English translation

Key Takeaways

The present infinitive is the main conjugation diagnostic: -āre, -ēre, -ere, and -īre. Combine it with the first-person singular, especially to recognize third-conjugation -iō verbs. The conjugation predicts present-system morphology; the third and fourth principal parts independently reveal perfect and supine stems. Read macrons as grammatical information, not optional decoration.