This is the 1712th most frequent Polish word.
rządzącej
"Rządzącej" means "ruling" or "governing" (referring to something or someone in power).
Here, "rządząca" is used as an adjective qualifying "partia," meaning "the ruling (party)."
Partia rządząca dzisiaj podejmowała ważne decyzje.
The ruling party made important decisions today.
Here, "rządzącej" modifies "partii" in the genitive case, showing possession: "of the ruling party."
Społeczeństwo dyskutuje o politykach partii rządzącej.
The society is discussing the politicians of the ruling party.
In this sentence, "rządzącej" is used to describe "liderki" in the genitive singular form, implying 'ruling' in relation to a female leader.