This is the 284th most frequent Polish word.
gdyż
"Because" or "since."
Here, 'gdyż' is used to provide a reason or explanation for not going for a walk.
Nie poszliśmy na spacer, gdyż zaczęło padać.
We didn't go for a walk because it started to rain.
In this sentence, 'gdyż' is used to explain the cause of her staying at home.
Została w domu, gdyż się źle czuła.
She stayed at home because she wasn't feeling well.
Here, 'gdyż' explains the justification for the decision to change the route.