This is the 346th most frequent Polish word.
ktoś
"Someone" or "somebody."
The word 'ktoś' is used here to indicate an unknown person who performed an action, translated as 'someone'.
Ktoś zapukał do drzwi.
Someone knocked on the door.
'Ktoś' is again used to refer to an unspecified or general person performing an action, implying that their identity is not specified or known.
Ktoś cię szukał, gdy byłeś na zewnątrz.
Someone was looking for you while you were outside.
'Ktoś' is used here to ask if any particular person (unspecified) is available to assist, translating directly to 'someone'.