Third-io Present Indicative | Latin Grammar

Third-iō verbs combine features of the third and fourth conjugations. Their first principal part ends in -iō, but their present active infinitive ends in short -ere: capiō, capere “take, capture,” not fourth-conjugation capīre. The resulting present has i in more places than regular third-conjugation regō, especially capiō and capiunt.

This “third-iō” or “mixed” label is a traditional description, not a separate semantic class. These verbs can mean taking, doing, fleeing, desiring, and much else. In ordinary Classical prose their present indicative is unmarked; only the forms are special.

Recognize the class from two principal parts

You need both the first and second principal parts. An -iō first person alone could belong either to third-iō or fourth conjugation; the infinitive settles the matter.

Principal parts	Infinitive test	Class	Meaning
capiō, capere, cēpī, captum	short -ere	third-iō	take, capture
faciō, facere, fēcī, factum	short -ere	third-iō	make, do
fugiō, fugere, fūgī, fugitum	short -ere	third-iō	flee, avoid
audiō, audīre, audīvī, audītum	long -īre	fourth	hear

For capiō, remove infinitive -ere to expose cap-, then add the mixed paradigm’s connecting vowels and endings. The label “present stem cape-” is also traditional, but it does not mean that visible e survives everywhere. The forms themselves must be learned as a pattern.

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Use a two-question diagnostic: does the first principal part end in -iō? If yes, does the infinitive have short -ere or long -īre? Short -ere means third-iō; long -īre means fourth conjugation.

Present indicative active

The active paradigm has i throughout. The third-person plural capiunt is especially diagnostic: regular third conjugation has regunt, while fourth conjugation also has audiunt but is identified by audīre.

Person	Form	Analysis	Possible English
1st singular	capiō	cap- + -iō	I take / am taking
2nd singular	capis	cap- + -i- + -s	you take / are taking
3rd singular	capit	cap- + -i- + -t	he/she takes
1st plural	capimus	cap- + -i- + -mus	we take / are taking
2nd plural	capitis	cap- + -i- + -tis	you all take
3rd plural	capiunt	cap- + -iu- + -nt	they take / are taking

Quid facis? Cēnam parō.

What are you doing? I am preparing dinner.

Cupiō tē nunc vidēre.

I want to see you now.

Pōcula capimus et ad mēnsam portāmus.

We pick up the cups and carry them to the table.

Puer lapidem in aquam iacit.

The boy throws a stone into the water.

Hostēs exercitum nostrum vident et statim fugiunt.

The enemy see our army and immediately flee.

As elsewhere in Latin, the endings normally make subject pronouns unnecessary. Cupiō is a complete clause, “I want”; ego cupiō makes the speaker contrastive. The present also leaves English aspect open: quid facis? naturally means “what are you doing?” even though Latin has no separate progressive auxiliary.

Present indicative passive

The passive retains the i pattern except in the second-person singular caperis/capere. The alternative capere is formally identical to the active infinitive “to take.” Context determines whether it is infinitive or finite passive.

Person	Form	Analysis	Basic English
1st singular	capior	cap- + -ior	I am taken
2nd singular	caperis / capere	cap- + -e- + -ris/-re	you are taken
3rd singular	capitur	cap- + -i- + -tur	he/she is captured
1st plural	capimur	cap- + -i- + -mur	we are captured
2nd plural	capiminī	cap- + -i- + -minī	you all are captured
3rd plural	capiuntur	cap- + -iu- + -ntur	they are captured

Fūr in viā ā custōdibus capitur.

The thief is caught in the street by the guards.

Tēla ex urbe in castra iaciuntur.

Missiles are being thrown from the city into the camp.

In proeliō ab hostibus capimur.

We are captured by the enemy in battle.

The nominative subject of a passive form receives the action. In fūr capitur, singular fūr controls singular capitur; the personal agent custōdibus stands in the ablative after ā. Compare active custōdēs fūrem capiunt: the guards become nominative, the thief accusative, and capiunt becomes active plural.

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Third-person plural is a quick voice contrast: capiunt means “they take,” while capiuntur means “they are taken.” The sequence -iu- belongs to both; passive -r distinguishes the second form.

The important exception: faciō

The active present of faciō follows third-iō: faciō, facis, facit, facimus, facitis, faciunt. Its passive, however, is supplied by fīō, fīs, fit, fīmus, fītis, fīunt “be made, become.” There is no productive Classical reason a learner can derive this suppletion from the English meaning; it must be learned with the lexical entry. Compounds in -ficiō, by contrast, generally have regular passives in -ficior, such as afficior.

Pānis hīc cotīdiē fit.

Bread is made here every day.

This is ordinary prose, not an archaic or poetic survival. For the full suppletive pattern, consult The Passive of Faciō: Fīō.

Tense value and register

The same present form can express an event underway, a habit, or a vivid past event. The historical present is especially common in (literary) narrative; an English translation often uses the past without changing the Latin parse.

Use	Latin	Natural English
current action	Nunc fugit.	He is fleeing now.
habit	Perīcula semper fugit.	He always avoids dangers.
general desire	Pācem cupimus.	We desire peace.
historical present (literary)	Dux gladium capit.	The commander took his sword.

Nunc gladium capit; herī arcum cēpit.

Now he takes up the sword; yesterday he took the bow.

The minimal contrast capit/cēpit is morphological. Capit belongs to the present system; cēpit uses the perfect stem from the third principal part. Do not select either merely because English “takes” or “took” seems familiar.

Parse before translating

For fugiunt, the -nt gives third-person plural active and the preceding -iu- points toward third-iō or fourth conjugation. The dictionary entry fugiō, fugere settles the class. With no other tense or mood marker, the form is present indicative active: “they flee/are fleeing.”

To produce “you all are captured,” choose passive, second-person plural and present indicative, then attach -minī to the pattern: capiminī. Beginning with these categories prevents English word order from generating an unnecessary form of sum.

Common Mistakes

1. Misclassifying an -iō verb as fourth conjugation

❌ Cupīmus domum redīre.

Incorrect for ‘we want to return home’ — cupere has short -ere and follows third-iō.

✅ Cupimus domum redīre.

We want to return home.

2. Dropping i in the third-person plural

❌ Custōdēs fūrem capunt.

Incorrect — third-iō has capiunt, not capunt.

✅ Custōdēs fūrem capiunt.

The guards catch the thief.

3. Forming the passive of faciō regularly

❌ Haec mēnsa ā fabrō facitur.

Incorrect Classical form for ‘this table is made’; faciō uses the suppletive passive fīō.

✅ Haec mēnsa ā fabrō fit.

This table is made by the craftsman.

4. Copying English “is doing” with two Latin verbs

❌ Puella est faciēns corōnam.

Incorrect as the ordinary present progressive ‘the girl is making a wreath.’

✅ Puella corōnam facit.

The girl is making a wreath.

Key Takeaways

Third-iō verbs are recognized by the combination first principal part -iō plus infinitive short -ere. Their present resembles third conjugation but keeps i in forms such as capiō, capiunt, and capiuntur. Learn faciō’s passive fīō as a genuine lexical exception, and always determine class, voice, person, and number before deciding how the form sounds in English.

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