This is the 294th most frequent Czech word.
kterém
"Kterém" means "which" or "in which" in English, used in the locative case.
Here, 've kterém' refers to the location where the action takes place (in the house).
Dům, ve kterém bydlím, je velmi starý.
The house in which I live is very old.
Here, 'o kterém' refers to the topic of discussion (the proposal).
Návrh, o kterém mluvíme, je velmi inovativní.
The proposal we are discussing is very innovative.
Here, 'na kterém' refers to the activity being carried out (on the project).