This is the 11723rd most frequent Swedish word.
penna
Penna: Pen.
Here, 'penna' refers to a writing instrument.
Jag skriver med en penna.
I write with a pen.
In this sentence, 'penna' refers specifically to an item (the pen) and is in its definite form 'pennan'.
Pennan ligger på bordet.
The pen is on the table.
Here, 'penna' refers to an unspecified writing instrument, indicated by the article 'en' meaning 'a'.