This is the 7913th most frequent Polish word.
moniki
"Moniki" is not a standalone word in Polish; it is typically the plural form of the name "Monika," referring to multiple people named Monika.
Here, 'moniki' is the genitive case of 'Monika', showing possession of the book.
Moniki książka jest bardzo interesująca.
Monika's book is very interesting.
In this example, 'Moniki' seems misplaced as it doesn't fit case-wise for 'I saw Monika'; it should be 'Monikę' in the accusative case. 'Moniki' could be a possessive or genitive plural form used incorrectly for the context.
Widziałem Moniki na spotkaniu wczoraj.
I saw Monika at the meeting yesterday.
'Moniki' is again in the genitive case indicating possession, referring to Monika's parents.