This is the 1547th most frequent German word.
ersten
"Ersten" is the dative singular or accusative plural form of "erste," meaning "first."
The word 'ersten' here is the masculine form of 'first' in nominative case modifying 'Versuch', meaning 'attempt'.
Das ist mein erster Versuch.
This is my first attempt.
'Ersten' here is used in dative case agreeing with 'Tag', indicating the temporal position of 'day'.
Am ersten Tag sind wir spazieren gegangen.
On the first day, we went for a walk.
The word 'ersten' is in dative case matched with 'Kapitel', referring to its sequence as 'first'.