Balaenoptera Physalus, commonly known as the fin whale, is a marine mammal that belongs to the family Balaenopteridae. This species is the second-largest animal on Earth after its close relative, the blue whale. The fin whale is also known by several other names that refer to its distinct physical features, such as razorback whale, common rorqual, and finback whale. The name razorback whale is attributed to the whale's prominent dorsal fin, which is located toward the posterior of its body. The common rorqual name refers to the species' ability to expand the ventral grooves or pleats that run from the throat to the navel while feeding. Finally, the name finback whale is derived from the whale's characteristic dorsal fin.