This is the 43rd most frequent Czech word.
korun
"Korun" is the genitive plural form of "koruna," the currency of the Czech Republic.
In this sentence, 'korun' denotes the currency used in the Czech Republic, specifically in its genitive plural form to indicate the amount of 100.
Zaplatil jsem sto korun za oběd.
I paid one hundred crowns for lunch.
Here, 'korun' again refers to the currency in its genitive plural form, used to indicate the amount (10) relative to the possession in the wallet.
Mám v peněžence jen deset korun.
I have only ten crowns in my wallet.
In this case, 'korun' continues to refer to the currency, appearing in the genitive plural form within an interrogative sentence asking about a price.