This is the 266th most frequent Russian word.
впервые
For the first time.
The word 'впервые' here emphasizes the occurrence of a new or once-unfelt emotion, highlighting its novelty to the subject's experience.
Она почувствовала себя счастливой впервые за долгое время.
She felt happy for the first time in a long while.
The word 'впервые' is used to indicate that this is the first time the subject has experienced or undertaken the action described by the verb.
В этом году я впервые посетил Петербург.
This year, I visited Petersburg for the first time.
In this sentence, 'впервые' points to the initial historical occurrence of a significant event or transformation.