This is the 50th most frequent Spanish word.
primera
"Primera" in English means "first" (feminine form).
Here, 'primera' describes 'impresión' as the initial or earliest in order relative to subsequent impressions.
La primera impresión es importante.
The first impression is important.
The word 'primera' is used here as an ordinal number modifying 'clase', indicating a rank in quality or priority.
Ella llegó en primera clase al evento.
She arrived in first class to the event.
Although 'primera' isn't used directly in this sentence, it demonstrates how ordinal numbers adapt in gender agreement, replacing it with 'primer' before 'paso' (masculine singular noun).