This is the 104th most frequent Polish word.
ponieważ
"Because" or "since" (used to indicate a reason).
Here, 'ponieważ' introduces a reason or cause of why the subject couldn't visit.
Nie mogłem do ciebie przyjechać, ponieważ musiałem pracować.
I couldn't come to you because I had to work.
'Ponieważ' is utilized to explain the justification for the subject's decision not to join.
On nie idzie z nami na spacer, ponieważ ma ważny egzamin jutro.
He is not coming with us for a walk because he has an important exam tomorrow.
In this sentence, 'ponieważ' links the inability to meet with the reason provided.