Some time ago, the term "fish" was used to categorise almost any water-dwelling creature - think shellfish, cuttlefish, starfish, etc.

Even dolphins and whales were categorised as fish at the time.

The term was later used mainly for "fin fish", which, as the name suggest, have fins or fin-like structures and are typically streamlined. This includes sharks which have a cartilage skeleton, as opposed to a bony one.

And then, a quote attributed to paleontologist Stephen Jay Gould purported that "there is no such thing as a fish".

It comes from the premise that "fish" are so biologically different from each other that it isn't quite right to place them all in the same category.

Of course, there are supporters, as well as opponents of this view. I'm not here to debate for one or the other.

I merely find the evolution of language and meaning fascinating, especially through different cultures and disciplines.

It reminds me that the words of today may mean something very different in the future, or may fall out of use entirely.