-ný / -tý (slovesné adjektivum)

The verbal adjective in -ný and -tý (often called the long passive participle) is a ubiquitous feature of everyday Czech. It allows you to compress a passive relative clause (e.g., "the letter that was written") into a single attributive adjective ("the written letter").

1. Formation
It attaches to the past stem of transitive verbs:

• -ný (or -ený/-ěný) is the default suffix for the vast majority of verbs: dělat → dělaný (done), otevřít → otevřený (open/opened). The massive -ovat verb class reliably forms the participle with -ovaný (e.g., kupovat → kupovaný = bought). Note that adding -ený/-ěný triggers widespread consonant mutations in the verb stem (e.g., t changes to c, d to z, s to š), such as platit → placený (paid), soudit → souzený (judged/tried), or nosit → nošený (worn).
• -tý is phonologically conditioned. It attaches to monosyllabic roots ending in a vowel (umýt → umytý = washed, vypít → vypitý = drunk up), some verbs ending in -nout (minout → minutý = missed/passed), and certain nasal roots (vzít → vzatý = taken).
• -nout verbs: While some take -tý, a large category of -nout verbs (those with a consonant before the suffix) drop the -nou- and take -ený with consonant mutations (e.g., táhnout → tažený = pulled). For example, zamknout (to lock) forms zamčený (locked), which is vastly more common in everyday Czech than the alternative zamknutý.
• Vowel shortening: Root vowels frequently shorten when forming this participle (e.g., psát → psaný = written, pít → pitý = drunk, mýt → mytý = washed, péct → pečený = baked).

2. Aspect, Meaning, and Negation
A common misconception is that this is strictly a "past" participle. Its meaning actually depends on the verb's aspect:

• Perfective verbs: Describe a completed, resultant state (napsaný dopis = the written letter).
• Imperfective verbs: Describe an ongoing state or general characteristic (milovaný = loved, vařený = boiled/being boiled).

Additionally, these verbal adjectives can be easily negated with the prefix ne- (e.g., napsaný → nenapsaný = unwritten), similar to standard verb negation with ne-. This is a very productive way to create negative adjectives.

3. Long vs. Short Forms
In formal written Czech, it is crucial to distinguish this from the short passive participle. The short form (otevřen) is used with the auxiliary verb být to form the verbal passive voice (Okno bylo otevřeno. = The window was opened). The long form (otevřený) is used attributively to modify a noun directly (otevřené okno = the open window) or as a state predicate (Okno je otevřené. = The window is open). However, in everyday spoken Czech, the long form routinely replaces the short form even for the verbal action passive (e.g., Ten dopis byl napsaný instead of byl napsán). Once formed, it declines exactly like standard hard adjectives.

4. Connection to Verbal Nouns
The stem of these verbal adjectives is also the exact foundation used to form Czech verbal nouns in -ní and -tí. You simply change the -ný/-tý suffix to -ní/-tí (e.g., psaný → psaní, umytý → umytí). Finally, note that some highly frequent verbs have irregular passive participles, such as jíst → snědený (eaten) and péct → pečený (baked).