"Kateřina bydlí v Čechách a Žofie na Moravě."

Translation: Kateřina lives in Bohemia and Žofie in Moravia.

[sjpet]

How come it's "v" for one and "na" for the other?

[VladaFu]

It is just like that. Some geographical places use "v", some "na". This usage can change in time and can differ between the standard language and common vernacular. It can differ between locals and speakers from other areas. There is no other way than learn each individually.

Note that an older variant was: "Dějiny národu českého v Čechách a v Moravě" (The history of the Czech nation in Bohemia and in Moravia)

"V" is much more common among different geographical names, so it is usually the safer bet.

"Na" for certain countries: na Slovensku, na Ukrajině, na Rusi (=the old Rus', Ruthenia),

"Na" for certain cities and towns: na Kladně, na Mělníce

various quarters of Prague: na Malé Straně, na Starém Městě (pražském), na Klárově, na Vinohradech, na Žižkově, na Karlově, na Vyšehradě, na Pankráci,... but v Libni, v Holešovicích, ve Strašnicích, v Košířích, v Troji (notice that some of those with "na" are located in or near the centre)

The relevant article (in Czech) http://prirucka.ujc.cas.cz/?id=640

[Paul747131]

Thank you! This helps.

[redkeel]

Thanks! In that article, it contrasts zima na horách vs zima v horách, but I'm not sure the difference in nuance between those. (Google translate gives both as 'winter in the mountains'). What's the difference in meaning between the two?

[VladaFu]

This is very subtle and despite Google being more often wrong than correct it really is both "in the mountains". We would have to discuss the preferences in individual very specific use cases. dovolená na horách, ukrytý vysoko v horách etc.