This is the 1136th most frequent Polish word.
rocznicę
"Rocznicę" means "anniversary" in English.
The word 'rocznicę' in this sentence is in the accusative case, as it is the direct object of the verb 'świętowaliśmy' (we celebrated). It refers to an anniversary.
Wczoraj świętowaliśmy naszą pierwszą rocznicę ślubu.
Yesterday, we celebrated our first wedding anniversary.
The word 'rocznica' here is in the nominative case, used to describe the subject of the sentence. It refers to an anniversary as a concept or event.
To była piękna rocznica, którą zapamiętam na zawsze.
It was a beautiful anniversary that I will remember forever.
The word 'rocznicę' is again in the accusative case, being the direct object of the phrase 'uczczać naszą rocznicę' (to celebrate our anniversary).