What do grammarians do for fun? Spot a new category of words, and then give them a name in Ancient Greek which no one else will understand.
What is it?
It's a word that describes a variety or type of something. An crow, for instance:
American crow, Corvus brachyrhynchos, photo by DickDaniels
is a variety of bird. So crow is a hyponym. A chair:
This looks comfy, doesn't it? Photo by didouner
is a type of furniture. So chair is a hyponym, too.
But the grammarians got double value out of this idea, because of course there's the group-word to name, too. A word that describes a group-of-things is called a hypernym. (Do please note the difficulty in distinguishing between those two words when spoken, but try not to let it annoy you too much.)
The article I've just read points out rather neatly that although at times the word screwdriver has the hypernym tool, at other times it has the hypernym cocktail.
What use are the terms hyponym and hypernym?
I'm not sure, to be honest. I mean, we've got on all right without them so far.
Thing To Consider Today: hyponyms and hypernyms. These words are both Greek. Hypo means under and hyper over. Onomas means name.