This is the 123rd most frequent Polish word.
jego
"Jego" means "his" or "him" in English.
In this sentence, 'jego' is a possessive pronoun indicating that the book belongs to 'him'.
Jego książka leży na stole.
His book is on the table.
Here, 'jego' functions as a pronoun serving as the object of the verb, meaning 'him'.
Nie widziałem jego dzisiaj.
I didn't see him today.
In this example, 'jego' emphasizes possession or relevance in context to 'his' opinion.