Language Adverbs: česky, anglicky, 'in Czech'

One of the first things you will want to say in Czech is "I speak Czech" — and one of the first surprises is that Czech does not use the noun for the language to say it. You do not "speak Czech" the way you would speak a noun; instead you "speak Czech-ly," using an adverb. The sentence Mluvím česky is, very literally, "I speak Czech-ly." This feels strange to an English speaker, because in English Czech is just a noun sitting after the verb. But the Czech logic is consistent and easy once you see it: the verb of speaking tells you how you speak, and how is the job of an adverb.

The rule: speaking a language takes the adverb

When the verb describes the manner of communicating — mluvit (speak), umět (be able to / know how), rozumět (understand), psát (write), číst (read), říct (say) — Czech uses the -sky / -cky adverb, not the noun.

The adverb is invariable — it never changes for gender, number, or case. Mluvím česky, mluvíš česky, mluvíme česky: the česky stays put while only the verb conjugates. This makes it one of the easiest things in Czech to use correctly, once you stop reaching for the noun.

Forming the adverb from the nationality adjective

The language adverb is built from the nationality adjective, which almost always ends in -ský / -cký. Drop the final -ý and you have the adverb in -sky / -cky.

So the chain is: český (the adjective, Czech) → česky (the adverb, in Czech) → and separately čeština (the noun, the Czech language). These three forms look alike but do different jobs, and confusing them is the heart of the difficulty. This is the same -sky/-cky adverb covered in adverb formation — language adverbs are simply the most useful subset.

When the noun comes back: the language as an object of study

The noun (čeština, angličtina, němčina, francouzština) is not wrong — it is just for a different job. Use the noun when the language is a thing you point at: a subject you study, a system you describe, the grammatical object of verbs like učit se (learn), studovat (study), znát (know — as a body of knowledge), or the subject of a sentence describing the language itself.

Compare the two halves of the system directly:

The dividing line is the verb. mluvit, umět, rozumět, psát, číst → adverb. učit se, studovat → noun. So Mluvím česky but Učím se češtinu: same language, two forms, chosen by the verb in front of them.

"How do you say … in Czech?"

The adverb also answers the question "in (a given language)" with verbs of saying. The very useful phrase for asking how to express something is built on česky:

Again the adverb, not the noun: you are asking how — in what manner, in which language — something is said.

A note on umět vs. mluvit

Both umět and mluvit take the language adverb, but they say slightly different things. Mluvím česky reports that you are, in fact, speaking Czech (or speak it in general). Umím česky reports a skill — "I can speak Czech, I know how." In an introduction, Umíte anglicky? ("Can you speak English?") is the natural way to ask whether someone has the ability, and it is covered alongside the other ability verbs on the umět / moci / znát page.

Common Mistakes

The errors here are almost all the noun-for-adverb swap that English transfer produces.

Key Takeaways

• To speak / understand / read / write a language, use the adverb in -sky/-cky: Mluvím česky.
• To learn / study a language, or to name it as a subject, use the noun: Učím se češtinu.
• The adverb is invariable — it never changes form.
• Build the adverb from the nationality adjective: český → česky, anglický → anglicky.
• The deciding factor is the verb: mluvit/umět/rozumět → adverb; učit se/studovat → noun.