Everything English

Whether is a conjunction used to introduce two alternatives, one of which may be implied, as in:

• Whether we go out or dine in, we are sure to have a pleasant evening.
• Regardless of whether she likes it, she will have to read it.
• I wonder whether it will rain today.

Sometimes, “whether” is followed by “or not” – but not always (often, “or not” is redundant, as the possibility of “or not” is implied). A few examples of when “or not” is necessary:

• Whether or not he meets with his professor, he will have to present on Monday.
• The conference will be held tomorrow, whether or not the room is prepared.

Note that these sentences could be written as:

• Whether he meets with his professor or not, he will have to present on Monday.
• The conference will be held tomorrow, whether the room is prepared or not.

In general, and as noted in an excellent New York Times article on the topic of “whether”, “or not” is needed when “whether” is meant to imply “regardless of whether”.