This is the 7172nd most frequent Polish word.
jacek
"Jacek" is a Polish male given name, equivalent to "Hyacinth" in English.
The proper noun for a person's name, 'Jacek'.
Jacek poszedł do sklepu.
Jacek went to the store.
The possessive form to indicate something authored by 'Jacek'.
Mam książkę autorstwa Jacka.
I have a book authored by Jacek.
The locative case form of 'Jacek'. This usage occurs because of the preposition 'o' (about), which necessitates the locative form.