This is the 203rd most frequent Ukrainian word.
серпня
"Серпня" in English means "August" (genitive case).
The word 'серпня' is used here in its genitive form to indicate that the vacation is scheduled at the beginning of the month referred to as August.
Ми плануємо відпочинок на початку серпня.
We are planning a vacation at the beginning of August.
In this sentence, 'серпня' is in the nominative case as it is the subject of the sentence, referring to the month August.
Серпня є важливим місяцем для збору врожаю.
August is an important month for the harvest.
Here, 'серпня' appears in locative form ('у серпня'), discussing something about the month happening within that timeframe, and showing how Ukrainian uses prepositions to modify case usage.