Why is the fin whale called whale?

The fin whale is called a "whale" because it belongs to the order Cetacea, which encompasses all whales, dolphins, and porpoises.

Here's a breakdown:

* Whale is a broad term referring to the large, aquatic mammals in the order Cetacea.

* Fin whale is a specific species within this order, distinguished by its long, thin fins and other physical characteristics.

So, the fin whale is a "whale" because it's a member of the same taxonomic group as all other whales.