This is the 4878th most frequent Polish word.
pachnie
"Smells" or "is fragrant."
In this sentence, "pachnie" is used to describe the pleasant scent emitted by the flower.
Kwiat w pokoju pachnie pięknie.
The flower in the room smells beautiful.
The word "pachną" (third-person plural form) indicates the scent coming from the person's perfume being delightful.
Twoje perfumy pachną wspaniale.
Your perfume smells wonderful.
In this usage, "pachnie" is used inquiringly to suggest the recognition of an unpleasant odor resembling burning.