This is the 116th most frequent Serbian word.
септембра
"Септембра" means "in September" in English.
This uses 'септембар' in the locative case to indicate the time 'in September'.
Школска година почиње у септембру.
The school year starts in September.
Here, 'септембар' is in the genitive case to indicate a time limit 'by September'.
Завршио сам пројекат до септембра.
I finished the project by September.
The word 'септембра' is in the genitive case to indicate possession or specification related to the day.