This is the 12314th most frequent Portuguese word.
secretamente
Secretly.
In this sentence, 'secretamente' describes the manner (adverb) in which the person looked at the letter, emphasizing it was done in a private way without others knowing.
Ela secretamente olhou para a carta antes de dobrá-la novamente.
She secretly looked at the letter before folding it again.
Here, 'secretamente' is used to describe the individual's action (adverbial usage), implying he was making this effort without public knowledge or in private.
Ele se esforçava secretamente para aprender uma nova habilidade.
He secretly strove to learn a new skill.
In this instance, 'secretamente' conveys the clandestine nature of the planning, highlighting the intention to keep it hidden from the person being surprised.