Whales are fish actually (and by “actually” I mean cladistically). And birds are reptiles (dinos specifically).
And all of the “such and such isn’t a vegetable, it’s a [fruit/berry/leafy green/brassica cultivar/pair of corduroys]” is also wrong since vegetable is only a culinary term, not a cladistic term.
And Frankenstein (the monster, not his eponymous creator) has been called that, at least since the 1927 play and the 1935 Bride of Frankenstein movie.
Vegetable is only a culinary term, not a cladistic one, although in the latter realm it is often used as a 1:1 synonym to plants (which would mean that bananas grow on a vegetable and so do acorns).
Let me try to phrase it another way.
“Vegetable” is a word of the kitchen, along with words like “shellfish” or “stir-fried” or “julienne”. It’s a culinary word.
(In biology “vegetable” can also sometimes mean all plants ever, including fruit.)
In the culinary realm, fruits are sweet and big like bananas, oranges, apples, while vegetables are less sweet like carrots, broccoli, cucumber.
Botanically cucumber and watermelon are closely related. Culinarily one is a vegetable and the other is a fruit.
Botanically, wheat and hazelnuts and tomatoes and corn are all fruit. When people go “well actually, tomatoes are a fruit, not a vegetable” they’re misusing vegetable in one of two ways. Most likely, the person they were trying to correct was using “vegetable” in the culinary sense, the kitchen sense. Or, less common, the person was using it in the “all plants” sense. (Either way, they were correct to call it a vegetable.)
So in the kitchen, things are one thing, and in the world of genes and nerds and botany, it’s another, but, that botany world:
Kitchen lingo has its own sets and subsets, like cinnamon and pepper are both “spices” without being particularly closely related botanically.
Malin wrote in with a link to a similar topic.