This is the 806th most frequent Dutch word.
aangezien
"Since" or "because."
In this sentence, 'aangezien' indicates the reason for not going, equivalent to 'since' or 'as' in English.
Hij wilde niet naar het feest gaan, aangezien hij zich niet goed voelde.
He didn't want to go to the party as he wasn't feeling well.
Here, 'aangezien' provides the reasoning for the suggestion, acting as 'while' or 'since' in a conditional sense.
Aangezien je nu toch bezig bent, kun je mij ook even helpen?
Since you're already busy with it, could you also help me?
Here, 'aangezien' is used to introduce a causal relationship; it means 'since' or 'because'.