This is the 2037th most frequent German word.
nationalen
"Nationalen" means "national" (plural or genitive singular form) in English.
Here, 'nationalen' is used as an adjective describing the word 'Symbol', denoting something related to the nation or country.
Das nationale Symbol der Freiheit ist die Flagge.
The national symbol of freedom is the flag.
In this sentence, 'nationalen' acts as an adjective modifying 'Feiertage', emphasizing that the holidays pertain to the nation.
Die nationalen Feiertage sind für die Geschichte unseres Landes bedeutend.
The national holidays are important for the history of our country.
Here, 'nationalen' is functioning as an adjective describing 'Interessen', denoting interests that represent the nation's concerns.