This is the 107th most frequent Serbian word.
августа
"Августа" means "August" (the month) in English.
In this sentence, 'августа' refers to the month August as the subject of the sentence.
Августа је последњи летњи месец у години.
August is the last summer month of the year.
Here, 'августа' is in the genitive case to indicate the date within the month.
Данас је трећи дан августа.
Today is the third day of August.
In this context, 'августа' is in the genitive case to specify the time frame within the month.