possum, "I can", and the infinitive
possum, potes, potest; the infinitive that completes a verb, takes a subject, or acts as a noun.
LatinIntermediate Latin · The perfect tensesAbout 3 min: 1 reading, 2 practiceUpdated
- Conjugate possum in every tense
- Use the complementary infinitive
- Put the subject of an infinitive in the accusative
- Use the infinitive as a neuter noun
Latin Level 2: verbs and the other declensions: lesson 18 of 35
- Intermediate Latin · Verbs: the present system
- sum: I am, I was, I shall be 3 min
- The present of amō and moneō 4 min
- The imperfect: was doing 4 min
- The future: will do 3 min
- The dative with adjectives 3 min
- The present of regō and audiō 4 min
- The imperfect of regō and audiō, and verbs that take the dative 3 min
- The future of regō and audiō 3 min
- capiō, and giving orders 3 min
- Intermediate Latin · The passive voice
- The passive: being done to 3 min
- The passive of regō, audiō and capiō; passive infinitives 3 min
- Synopses, and the ablative of "from" 3 min
- Intermediate Latin · The perfect tenses
- fuī, fueram, fuerō: the perfect tenses of sum 3 min
- The perfect active: did, have done 5 min
- Had done, will have done: pluperfect and future perfect active 3 min
- amātus sum: the perfect passive 4 min
- Principal parts, prepositions, and yes-or-no questions 5 min
- possum, "I can", and the infinitive 3 min
- Intermediate Latin · Pronouns
- quī, quae, quod: who, which, that 4 min
- Intermediate Latin · The third declension
- rēx, rēgis: the third declension 4 min
- hostis, urbs, mare: i-stems 4 min
- vīs and iter; gender in the third declension 4 min
- omnis, ācer, pār: third-declension adjectives 3 min
- Intermediate Latin · The fourth and fifth declensions
- manus, cornū: the fourth declension 3 min
- Rōmae, domī, Athēnīs: place and the locative 4 min
- diēs, rēs: the fifth declension and the ablative of time 3 min
- Intermediate Latin · Pronouns
- ego, tū, sē: personal and reflexive pronouns 4 min
- ipse, "himself", and īdem, "the same" 3 min
- hic, iste, ille: this and that 4 min
- aliquis, quīdam, quisque: someone, a certain, each 3 min
- Intermediate Latin · Comparison
- clārior, clārissimus: comparing adjectives 4 min
- melior, optimus: irregular comparison, plūs, and "by how much" 3 min
- clārē, fortiter: adverbs and their comparison 4 min
- Intermediate Latin · Numerals
- ūnus, duo, trēs: numerals, "of" the whole, and "for how long" 5 min
- Intermediate Latin · Deponent verbs
- hortor, sequor: deponent verbs 3 min
Try first
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Pairs with D'Ooge, Latin for Beginners (Ginn, 1909), Lesson XXXVII ("Conjugation of possum · The Infinitive Used as in English"), §§ 212–216
What it is
Possum is pot- ("able") + sum. Before a vowel it is pot-, before s it becomes pos-:
| Present | Imperfect | |
|---|---|---|
| I | possum | poteram |
| you | potes | poterās |
| he/she | potest | poterat |
| we | possumus | poterāmus |
| you pl. | potestis | poterātis |
| they | possunt | poterant |
Future: poterō, poteris, poterit, poterimus, poteritis, poterunt.
Principal parts: possum, posse, potuī. Perfect potuī, pluperfect potueram, future perfect potuerō; perfect infinitive potuisse.
The infinitive is used three ways:
- Completing a verb (complementary): Rōmānī Gallōs superāre possunt. → The Romans can overcome the Gauls.
- With a subject in the accusative, after verbs like "order": Is virōs fugere iussit. → He ordered the men to flee.
- As a noun, neuter singular: Vidēre est crēdere. → To see is to believe.
Quick check
Tap an answer to check it.
"They were able"
- Present: they are able
Show answer
poterant. Imperfect of possum: poteram, poterās … poterant.
Why it matters
"Can", "order someone to", "to … is …": these are everyday patterns. Iubeō + accusative + infinitive is also the first step towards indirect speech, one of the biggest constructions in Latin.
Worked example
- Puerī labōrāre nōn possunt. → The boys cannot work.
- Lēgātus cōpiās venīre iussit. → The lieutenant ordered the troops to come. (cōpiās: accusative, the subject of venīre)
- Superāre est grātum. → To conquer is pleasing. (grātum: neuter, agreeing with superāre)
Common mistake
Putting the subject of the infinitive in the nominative: wrong: Lēgātus cōpiae venīre iussit. After iubeō, the person told to act is accusative: cōpiās venīre iussit.
Key terms
- possum, posse, potuī
- be able, can
- complementary infinitive
- completes a verb: possum vidēre
- subject accusative
- the subject of an infinitive is accusative
- iubeō, iubēre, iussī, iussus
- order
- grātus, -a, -um
- pleasing
Practise the key terms
Tap a card to turn it over. 5 cards.
| Front | Back |
|---|---|
| possum, posse, potuī | be able, can |
| complementary infinitive | completes a verb: possum vidēre |
| subject accusative | the subject of an infinitive is accusative |
| iubeō, iubēre, iussī, iussus | order |
| grātus, -a, -um | pleasing |
Practice
Quick quiz
Tap an answer to check it.
"We can see the town."
- possum is completed by an infinitive
Show answer
Oppidum vidēre possumus.. Complementary infinitive: vidēre.
"He ordered the boys to come."
- The subject of the infinitive is accusative
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Puerōs venīre iussit.. Subject of the infinitive: accusative.
"You (one) will be able"
- Present: you are able
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poteris. Future of possum: poterō, poteris …
Build the sentence
"The Romans can overcome the Gauls." Put the subject first, then the object, then the infinitive, then the verb.
Show answer
Rōmānī Gallōs superāre possunt
Practise speaking
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You are a patient Latin tutor. Use the classical pronunciation only, never the Church one: c is always k, g is always hard, v sounds like w, ae like the ai in aisle, and long vowels are held longer. Speak slowly. Use only these Latin words: possum, potes, potest, possumus, potestis, possunt, poteram, poterō, iubeō, iussit, venīre, vidēre, superāre. Give me English sentences like 'we can see the town', 'they were able to come' or 'he ordered the boys to come', and I will say them in Latin. Do 8 sentences. After each answer, tell me what kind of mistake I made, if any, and let me try again, then tell me one thing to improve. Keep every reply under 2 sentences. If I need a name or a town, I will make one up. Speak English except for the Latin itself.
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Good to know. AI feedback on pronunciation is hit and miss, so check yourself against native recordings. This course teaches the classical pronunciation (see lesson 1); AI voices may mix it with the Church (Italian-style) one, so ask for classical and check against lesson 1. Don't share personal details: use a made-up name and town.
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In short
- possum = pot- + sum; pos- before s: possum, potes, potest, possumus, potestis, possunt.
- Perfect potuī; infinitive posse.
- Infinitive completes a verb: possum vidēre.
- Subject of an infinitive: accusative (iussit virōs fugere).
- Infinitive as a noun: neuter singular (vidēre est crēdere).
Mastery check
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Check yourself
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Give "they will be able".
Show answer
poterunt.
Translate Vidēre est crēdere.
Show answer
To see is to believe (seeing is believing).
Why is puerōs accusative in Puerōs venīre iussit?
Show answer
It is the subject of the infinitive venīre.
Further reading
- D'Ooge, Latin for Beginners, Lesson XXXVII, §§ 212–216. Public domain; Project Gutenberg.
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