za + Accusative

When the preposition za governs the accusative case, it has several extremely common uses, including:

1. Time (Elapsed or Completed)

• Future Gap: It expresses how much time will pass before an event happens (English "in"). Example: Přijdu za hodinu. (I will come in an hour.)
• Completion Span: It expresses how long it took to complete a finished action (English "in" or "within"). Example: Udělal to za hodinu. (He did it in an hour.)

2. Price, Exchange, and Substitution

• Price: Used with verbs of transaction like koupit (to buy) or prodat (to sell) to state the price. Example: Koupil to za sto korun. (He bought it for 100 crowns.)
• Exchange/Gratitude: Used when trading one thing for another, or expressing thanks. Example: Děkuji za pomoc. (Thank you for the help.)
• Substitution: Used when doing something instead of someone else. Example: Udělám to za tebe. (I will do it for you / instead of you.)

Note: Do not confuse za with pro. Use za for exchange or price, but use pro for the beneficiary (e.g., a gift for someone).

3. Frequency and Rate

• Frequency: Expresses how often something happens within a given time period. Example: Cvičím dvakrát za týden. (I exercise twice a week.) Note that the adverbial form dvakrát týdně is also very frequently used.
• Rate: Expresses speed or rate. Example: Jel sto kilometrů za hodinu. (He drove 100 kilometers per hour.)

4. Advocacy and Representing

• Fighting/Playing For: Used to express support, advocacy, or representing a group. Example: Bojují za svobodu. (They are fighting for freedom.) or Hraje za Spartu. (He plays for Sparta.)

5. The "What kind of..." Idiom

• Co je to za...: A very common conversational idiom used to ask "What kind of [noun] is that?" Example: Co je to za člověka? (What kind of person is that?)

6. Regarded As and Fixed Verbs

• Considered As: Used with verbs like považovat (to consider) or mít (to have/consider). Example: Mám ho za přítele. (I consider him a friend.)
• Fixed Phrases: Used in common expressions like stát za to (to be worth it), vdát se za (to marry - for a woman), omluvit se za (to apologize for), stydět se za (to be ashamed of), modlit se za (to pray for), or prosit za (to plead/beg for).

7. Spatial Motion and Grasping

• Motion Behind: Expresses movement to a position behind something, answering the question kam? (where to?). Example: Šel za dům. (He went behind the house.) Note: za + accusative is strictly for motion/destination. For static location answering kde? (where?), you must use the instrumental case (e.g., Jsem za rohem. - I am behind the corner).
• Holding/Taking: Used when taking or holding someone or something by a specific part. Example: Vzal ji za ruku. (He took her by the hand.)
• Important Warning for Visiting People: When expressing motion toward a person (going to see or visit someone), you must use za + instrumental case (e.g., Jdu za kamarádem. - I am going to see a friend). If you use the accusative here (Jdu za kamaráda.), it means substitution (I am going instead of a friend).

Important Note on Numbers:
When using za with quantities (like minutes or crowns), standard Czech numeral rules apply. For quantities 1–4, the noun stays in the accusative (za dvě hodiny). For quantities of 5 or more, the numeral takes the accusative, but it forces the following noun into the genitive plural (za pět hodin). You can learn more about this in genitive plural after five and higher numerals.