This is the 1794th most frequent Portuguese word.
inteiro
Whole; entire; complete.
In this sentence, 'inteiro' is used as an adjective describing the entirety of the cake, indicating that no portion of it was left uneaten.
Eu comi o bolo inteiro.
I ate the whole cake.
Here, 'inteiro' is used to emphasize that the action of studying occupied the entire day. It's also an adjective modifying 'dia', providing a complete duration aspect.
Ele passou o dia inteiro estudando.
He spent the whole day studying.
In this usage, 'inteiro' describes the state or condition of the document, meaning that it remains intact (unbroken or undamaged).