Kathleen from Hebron, Connecticut, is curious about the term hashtag. She associates it with the symbol #, which she calls a pound sign. When that symbol, also known as a hash mark, doublecross, hatch mark, octothorpe, or number sign, is appended to a keyword, the whole thing is known as a hashtag. It’s used on Twitter, among other places, to help label a message on a particular topic. This is part of a complete episode.