This is the 4465th most frequent Russian word.
волноваться
To worry or to be anxious.
Here, 'волноваться' is used to mean 'worry' in the sense of being concerned about something.
Не нужно волноваться, всё будет в порядке.
You don't need to worry, everything will be fine.
In this sentence, 'волноваться' is employed to express 'beginning to feel anxious' due to specific circumstances.
Она начала волноваться из-за экзаменов.
She started to worry about the exams.
Here, 'волноваться' conveys feeling anxious or uneasy, specifically in anticipation of an upcoming event.