This is the 525th most frequent Polish word.
pani
"Mrs." or "Ms." (a polite form of address for a woman).
'Pani' here denotes the polite form of address matched with a surname, indicating respect or formality.
To jest książka pani Kowalskiej.
This is Mrs. Kowalska's book.
In this context, 'pani' is used as a title before a given name, also indicating respect or formality, much like 'Mrs.' or 'Ms.' in English.
Pani Anna jest dzisiaj nieobecna.
Mrs. Anna is absent today.
Here, 'pani' is used as a polite address to a woman, equivalent to 'ma'am' or 'Mrs.' in English.