This is the 4368th most frequent Russian word.
будь
"Будь" means "be" (imperative form).
In this sentence, "будь" is used as an imperative form of the verb "быть" (to be), used to express a command or directive.
Будь внимателен на дороге.
Be attentive on the road.
Here, "будь" is part of a conditional suggestion, encouraging confidence.
Если у тебя будут вопросы, будь уверен, что можешь их задать.
If you have questions, be sure that you can ask them.
In this example, "будь" is used in a hypothetical or stipulative scenario, introducing alternatives or options.