rozumět / porozumět — to understand

"To understand" is rozumět / porozumět. By far the most useful thing to know about this verb is not its conjugation but its case: in Czech you understand to something, not understand it — the thing understood goes in the dative. Rozumím ti ("I understand you"), Rozumím češtině ("I understand Czech"), Nerozumím té otázce ("I don't understand that question"). English speakers instinctively reach for a direct object and produce the wrong case; making the dative automatic is the single biggest win on this page.

The two halves, side by side

Both verbs belong to Class IV (the -ět / -ím type, like trpět and umět). The perfective simply adds the prefix po-.

The third-person plural has two forms. The standard literary ending is rozumějí (like umějí, smějí); the shorter rozumí is extremely common in speech and is also accepted. Past tense: rozuměl, rozuměla, rozumělo, rozuměli, rozuměly, rozuměla. Imperative: rozuměj / rozumějte.

The core point: the dative of what is understood

In English, "understand" takes a direct object: understand you, understand the question, understand Czech. In Czech, the object of rozumět stands in the dative. There is no preposition — just the bare dative noun or pronoun.

ti is the dative of ty. Compare the accusative tě ("you" as a direct object): Rozumím ti is correct, Rozumím tě is wrong. The dative is the whole game here.

tomu textu is the dative of ten text. Notice the demonstrative agrees: dative tomu, not accusative ten.

nářečí is the dative (here identical to the nominative, as neuter -í nouns don't change) — but the grammar is still dative; you can see it clearly when the noun is something like češtině (dative of čeština) or Petrovi (dative of Petr).

Here té větě is unmistakably dative (ta věta → té větě), which is exactly why this example is worth saying out loud a few times — it trains the case into your ear.

rozumět si — to understand one another

With the reflexive dative si, rozumět means "to get along, to understand each other" — a very common idiom about relationships, not just comprehension.

rozumět vs chápat — two kinds of understanding

English "understand" covers two ideas that Czech splits. rozumět is to understand in the sense of following something — a language, words, a person, instructions. chápat / pochopit is to grasp, comprehend, make sense of — to understand why or how. Crucially, chápat governs the accusative, like a normal transitive verb.

This sentence puts both verbs in one breath: rozumím + dative (každému slovu, "every word") for following the language, nechápu + accusative clause for grasping the intention. They are not interchangeable — and the case flips with the meaning.

Common mistakes

This is the signature error. Tě is accusative; rozumět demands the dative ti. Whenever the object of rozumět is a person or a thing, put it in the dative.

The accusative tu otázku (direct-object form) is what English leads you to. Czech needs the dative té otázce.

When you mean "I grasp the reason / it makes sense to me," Czech reaches for chápat (accusative), not rozumět. Both are understandable, but chápat is the natural choice for comprehending a why.

Understanding a language is an ongoing state, so it is imperfective: Rozumím česky. The perfective porozumět would mean a one-time act of coming to understand, which is not what "I understand Czech" expresses.

Key takeaways

• rozumět = imperfective (the state of understanding); porozumět = perfective (the moment of coming to understand). The default is the imperfective.
• The thing understood goes in the dative, with no preposition: Rozumím ti, Rozumím češtině, Nerozumím té otázce.
• This is one of the most reliable transfer errors for English speakers — drill Rozumím ti, never Rozumím tě.
• rozumět si (+ dative si) = "to get along / understand one another."
• For grasping a reason or making sense of something, prefer chápat / pochopit, which takes the accusative.