This is the 174th most frequent Serbian word.
децембра
"Децембра" means "in December" in English.
The word 'децембар' is used as a noun referring to the month of December.
Данас је хладно јер је већ децембар.
Today is cold because it's already December.
Here, 'децембра' is used in its genitive form to indicate 'of December' in a locative context.
Трг је украшен светлима почевши од децембра.
The square is decorated with lights starting from December.
In this case, 'децембра' is used in a time expression context clarifying the temporal setting of the action.