whether
US /ˈweð.ɚ/
UK /ˈweð.ɚ/

1.
si
expressing a doubt or choice between two alternatives
:
•
I'm not sure whether I should go or stay.
No estoy seguro si debo ir o quedarme.
•
She asked whether he was coming to the party.
Ella preguntó si él vendría a la fiesta.
2.
si
introducing an indirect question, often with 'or not' implied
:
•
Let me know whether you can make it.
Avísame si puedes venir.
•
It doesn't matter whether it rains or shines.
No importa si llueve o hace sol.