Whale
People use the word whale in different ways.  Some use it for all Cetaceans including dolphins and porpoises.  These people say that dolphins and porpoises are also whales, because they are also Cetaceans.  Others separate out the dolphins and porpoises: common English-speaking people have never called them or thought of them as whales unless they are very large.  Actually, there is no clear line between whales and dolphins.