The word "whether" is a conjunction used to introduce alternatives or choices. It often presents a condition or indicates doubt between two or more possibilities. For example, when someone is deciding between two options, you might ask them, "Are you going to the party, whether it rains or not?"
The word "whether" comes from Old English "hwæðer," which means "which of the two." It is related to the word "whether" in German ("weder"), and it has been used in English since before the 12th century.