do + Genitive (Direction)

1. When to use "do"
Use do to answer the question Kam? (Where to?) for movement into enclosed spaces (rooms, buildings), cities, and most countries. You will typically use this with verbs of motion such as jít (to go on foot), jet (to go by vehicle), cestovat (to travel), and letět (to fly), as well as verbs of placement like dát (to put), which also answer Kam? (e.g., dát do tašky - to put into a bag). If you would say you are "in" (v / ve) a place once you arrive, you use do to get there. The opposite of going do (into) a place is coming z / ze (out of/from) it. Note that some countries and regions use na instead (e.g., na Slovensko, na Moravu, or islands like na Island). Similarly, if a destination uses na for motion (e.g., na poštu), it will pair with na for location (na poště).

2. The Grammar and Pronunciation
The preposition do forces the following noun, pronoun, or adjective into the genitive case (2. pád). You will become comfortable with all the endings over time, but here are the most common changes for nouns:

• Feminine nouns ending in -a usually change to -y (Praha → do Prahy).
• Feminine nouns ending in -e / -ě do not change their ending in the singular (restaurace → do restaurace, práce → do práce).
• Masculine inanimate nouns often add -u or -a (obchod → do obchodu, les → do lesa).
• Neuter nouns ending in -o change to -a (město → do města).
• Neuter nouns ending in -í do not change their ending (zahraničí → do zahraničí).
• For plural destinations, the genitive often drops the final vowel or adds -ů (hory → do hor, Čechy → do Čech, Spojené státy → do Spojených států).

When speaking, a one-syllable preposition like do forms a single prosodic unit with the following word, pulling the word stress onto the preposition (e.g., DO práce, DO lesa).

3. Important Rules and Concepts

• When expressing that you are going to visit someone or going to their place, do not use do. To say "I am going to the doctor," you must use k / ke.
• While na (+ accusative) is the standard preposition for events (e.g., na koncert) and open surfaces (e.g., na náměstí), places like do lesa (to the forest) and do parku (to the park) use do. Czech conceptualizes these as 3D "containers" where you are surrounded by trees.
• A crucial vocabulary exception to memorize is do práce (to work), which takes do even though it is an abstract activity.
• Conversely, many public institutions idiomatically take na + accusative instead of do, even though they are enclosed buildings (e.g., na poštu, na nádraží, na policii).

4. Time Limits (Until / By)
While this pattern focuses on direction, do is also commonly used to express time limits, meaning "until" or "by" (answering the question Dokdy?). For example, do pátku (until Friday) or do večera (until the evening).