Whether
Definition 1 of 2
Pro Tip 1/3
Decision Making
Used when someone is uncertain and choosing between different options. She is deciding whether to travel by train or plane.
Pro Tip 2/3
Including Both
'Whether or not' means both possibilities are considered, regardless of the condition. I will attend the picnic whether or not it rains.
Pro Tip 3/3
Indirect Questions
When embedding a question within a statement, 'whether' is often used. Can you tell me whether the store is open?