This is the 2910th most frequent Spanish word.
séptimo
Seventh.
Here, "séptimo" is used as a cardinal ordinal number indicating the sequence of the chapter in the book.
Este es el séptimo capítulo del libro.
This is the seventh chapter of the book.
"Séptima" is used to modify the noun "clase", indicating its sequential order in the series of lessons.
Estamos preparándonos para nuestra séptima clase de baile.
We are preparing for our seventh dance lesson.
In this sentence, "séptimo" functions as an ordinal to designate the player's position in the queue.