Cognōscō means “learn,” “come to know,” “investigate,” or “recognize.” Its principal parts are cognōscō, cognōscere, cognōvī, cognitum. In this lexical family, present-system cognōsc- commonly profiles acquiring knowledge, while the perfect loses -sc- and cognōvī often means “I have learned, hence I know.” That contrast is lexical, not a rule that can be imposed mechanically on every Latin verb in -scō.
This aspectual contrast matters more than any one-word gloss. English normally says present “I know” where Latin may use the formally perfect cognōvī because the learning has reached its result.
Complete Active Paradigm
| Tense | 1st sg. | 2nd sg. | 3rd sg. | 1st pl. | 2nd pl. | 3rd pl. |
|---|---|---|---|---|---|---|
| Present | cognōscō | cognōscis | cognōscit | cognōscimus | cognōscitis | cognōscunt |
| Imperfect | cognōscēbam | cognōscēbās | cognōscēbat | cognōscēbāmus | cognōscēbātis | cognōscēbant |
| Future | cognōscam | cognōscēs | cognōscet | cognōscēmus | cognōscētis | cognōscent |
| Perfect | cognōvī | cognōvistī | cognōvit | cognōvimus | cognōvistis | cognōvērunt / cognōvēre |
| Pluperfect | cognōveram | cognōverās | cognōverat | cognōverāmus | cognōverātis | cognōverant |
| Future perfect | cognōverō | cognōveris | cognōverit | cognōverimus | cognōveritis | cognōverint |
The perfect system very often appears without -v-: cognōvistī → cognōstī, cognōveram → cognōram, cognōverim → cognōrim, and cognōvisse → cognōsse. These contractions are ordinary Classical forms, not different stems or tenses.
| Subjunctive | 1st sg. | 2nd sg. | 3rd sg. | 1st pl. | 2nd pl. | 3rd pl. |
|---|---|---|---|---|---|---|
| Present | cognōscam | cognōscās | cognōscat | cognōscāmus | cognōscātis | cognōscant |
| Imperfect | cognōscerem | cognōscerēs | cognōsceret | cognōscerēmus | cognōscerētis | cognōscerent |
| Perfect | cognōverim | cognōverīs | cognōverit | cognōverīmus | cognōverītis | cognōverint |
| Pluperfect | cognōvissem | cognōvissēs | cognōvisset | cognōvissēmus | cognōvissētis | cognōvissent |
Iūdex causam cognōscit.
The judge is investigating the case.
Paulātim mōrēs urbis cognōscēbāmus.
We were gradually getting to know the city’s customs.
Ex litterīs cōnsilium eōrum cognōvī.
From the letter I learned their plan.
Cum omnia cognōverit, sententiam dīcet.
When he has learned all the facts, he will state his opinion.
First-person cognōscam may be future indicative or present subjunctive. Context—not the ending alone—resolves the form.
Passive Voice
| Tense | 1st sg. | 2nd sg. | 3rd sg. | 1st pl. | 2nd pl. | 3rd pl. |
|---|---|---|---|---|---|---|
| Present | cognōscor | cognōsceris | cognōscitur | cognōscimur | cognōsciminī | cognōscuntur |
| Imperfect | cognōscēbar | cognōscēbāris | cognōscēbātur | cognōscēbāmur | cognōscēbāminī | cognōscēbantur |
| Future | cognōscar | cognōscēris | cognōscētur | cognōscēmur | cognōscēminī | cognōscentur |
| Present subjunctive | cognōscar | cognōscāris | cognōscātur | cognōscāmur | cognōscāminī | cognōscantur |
| Imperfect subjunctive | cognōscerer | cognōscerēris | cognōscerētur | cognōscerēmur | cognōscerēminī | cognōscerentur |
Perfect passive forms combine cognitus, -a, -um with sum: cognitus est, cognita erat, cognitī erunt; cognitus sit, cognita esset. Personal passives are ordinary when someone or something becomes recognized; impersonal cognōscitur is especially common in inquiry (formal/legal).
Fraus ex ūnā epistulā cognita est.
The fraud was discovered from a single letter.
Vultus amīcī in turbā statim cognōscitur.
A friend’s face is recognized at once in a crowd.
Commands and Non-Finite Forms
Present commands are cognōsce, cognōscite. Future imperatives cognōscitō, cognōscitōte, cognōscuntō and passive commands are (formal/archaic).
| Category | Active | Passive |
|---|---|---|
| Present infinitive | cognōscere | cognōscī |
| Perfect infinitive | cognōvisse | cognitum esse |
| Future infinitive | cognitūrum esse | cognitum īrī |
| Participles | cognōscēns; cognitūrus | cognitus; cognōscendus |
| Gerund | cognōscendī, cognōscendō, cognōscendum, cognōscendō | — |
| Supines | cognitum, cognitū | — |
Dux dīxit sē cōnsilium hostium cognōvisse.
The commander said that he had learned the enemy’s plan.
Nōbīs tōta causa cognōscenda est.
We must investigate the whole case.
Objects, Statements, and Topics
A person, fact, character, place, or case may be a direct object: hominem cognōscere, mōrēs cognōscere, causam cognōscere. A reported fact can appear as accusative-and-infinitive. A topic under investigation may use dē plus ablative, especially in legal or administrative prose.
Dē iniūriā cognōscere coepērunt.
They began to investigate the wrongdoing.
Cognōvimus mercātōrēs ante lūcem discessisse.
We learned that the merchants had left before dawn.
The perfect infinitive discessisse is earlier than cognōvimus. English “learned that” disguises the Latin accusative subject mercātōrēs and infinitive. See accusative-and-infinitive.
When what is ascertained is framed as a question rather than a proposition, an interrogative word introduces a subjunctive clause.
Iūdex cognōscere voluit quid testis vīdisset.
The judge wanted to ascertain what the witness had seen.
Process, Result, and Recognition
Present-system forms typically show knowledge being acquired: questioning witnesses, studying a place, or beginning to recognize a person. Perfect-system forms can report either the completed act of discovery or its continuing result.
Nunc tē cognōscō: eādem vōce ūtebāris.
Now I recognize you: you were using the same voice.
Eum iam diū cognōvī.
I have known him for a long time.
The second is formally perfect because acquaintance was acquired and remains. Do not force an English past merely because the Latin form is perfect. Conversely, sciō normally states knowledge without presenting its acquisition: rem sciō “I know the fact.”
Compounds and the -nōsc- Family
The broader -nōscō family has two visible stem patterns. Agnōscō, agnōvī, agnitum and recognōscō, recognōvī, recognitum retain -gnōsc- / -gnōv- / -gnit-; pernōscō, pernōvī, pernōtum and ignōscō, ignōvī, ignōtum instead show -nōsc- / -nōv- / -nōt-. Agnōscō means “recognize, acknowledge,” recognōscō “review, inspect, recognize again,” and pernōscō “learn thoroughly.” Ignōscō means “pardon” and takes a dative; its meaning and government must be learned separately.
Centuriō veterānum ex cicātrīce agnōvit.
The centurion recognized the veteran from his scar.
Dux captīvīs ignōvit.
The commander pardoned the captives.
The last sentence has dative captīvīs. Treating every member of the -nōscō family as “know” would miss a lexicalized meaning.
Evidence, Source, and Degree of Knowledge
Latin often states the evidence from which something is learned with ex plus ablative: ex litterīs cognōscere “learn from a letter,” ex vultū cognōscere “recognize from someone’s face.” The source phrase is not an agent; it identifies the sign or evidence that enables recognition. An ablative alone may occur in established contexts, but ex makes the relation transparent for learners.
Ex vestīgiīs cognōvimus equitēs per silvam trānsiisse.
From the tracks we learned that cavalry had passed through the forest.
Prefixes can intensify the completeness of learning. Pernōscere presents thorough acquaintance, while simple cognōscere does not itself promise that the investigation succeeded completely.
Ante iūdicium omnia documenta pernōscenda sunt.
Before the trial all the documents must be examined thoroughly.
This distinction matters for aspect: an imperfect investigation may remain unfinished, while perfect cognōvī normally presents discovery as achieved or knowledge as established.
Parsing Diagnostic
Look first for cognōsc-, cognōv-, or cognit-. The first points to the present system, the second to the active perfect system, and the third to participles, supines, or perfect passive forms. Contracted cognōstī, cognōram, cognōrim, and cognōsse still belong to the perfect system. Next decide whether context emphasizes investigation, recognition, completed discovery, or resulting knowledge.
Common Mistakes
Keeping -sc- in the perfect
❌ Tandem eum cognōscīvī.
Incorrect — the perfect stem is cognōv-.
✅ Tandem eum cognōvī.
At last I recognized him.
Translating every perfect as a past event
❌ Eum diū cognōvī.
Incorrectly understood as only ‘I met him long ago.’
✅ Eum diū cognōvī.
I have known him for a long time.
Using sciō for an investigation in progress
❌ Iūdex causam scit.
Wrong for ‘the judge is investigating the case’: this says that he knows it.
✅ Iūdex causam cognōscit.
The judge is investigating the case.
Giving ignōscō an accusative person
❌ Pater fīlium ignōvit.
Incorrect — the person forgiven is dative.
✅ Pater fīliō ignōvit.
The father forgave his son.
Key Takeaways
- Memorize cognōscō, cognōscere, cognōvī, cognitum.
- Present cognōsc- often profiles acquisition; perfect cognōv- can express resulting knowledge.
- The verb takes direct objects, accusative-and-infinitive statements, and dē topics in inquiry.
- Compounds preserve the stem alternation but may change meaning and government.
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Start learning Latin →Related Topics
- Scio: To KnowA2 — A complete reference for sciō, including its full paradigm, ways of expressing known facts, passive forms, and contrast with cognōscō.
- Nescio: Not to KnowA2 — A complete reference for nesciō, including its paradigm, indirect questions, indefinite nescio quis phrases, passive forms, and usage contrasts.
- Inceptive Verbs in -scoB2 — Recognize Latin -scō verbs as lexical verbs of entering or developing a state, and follow their stem changes across the verbal system.
- Accusative Subject of the InfinitiveA2 — Recognize the accusative noun or pronoun that serves as the subject inside a Latin infinitival clause.