This is the 909th most frequent Czech word.
rusů
"Rusů" is the genitive plural form of "Rus," meaning "Russians" in English.
In this sentence, 'Rusů' is used as a genitive plural form of 'Rus', which refers to people from Russia (Russians). This form is used to indicate possession or association (culture of the Russians).
Mluvili jsme o kultuře Rusů.
We talked about the culture of Russians.
In this context, 'Rusů' is again the genitive plural form, describing something attributed to or owned by the group of people referred to as 'Russians'.
Památky Rusů svědčí o jejich bohaté historii.
The monuments of the Russians testify to their rich history.
Here, the word 'Rusů' does not appear directly, but the context is similar. If we wanted to describe the group possessive or related to them, 'Rusů' would be applicable. However, this sentence uses 'Rusy' (accusative plural), which changes the focus slightly.