Are circles special types of ellipses/ovals?
Are cones special types of pyramids? I guess the answer is no because of the 2D basis: circles are not special types of however you categorise the bases of pyramids. However, cubes are cuboids/(right?) rectangular prisms because
Why/why not to all of the above? How do we know if a certain thing is a special type of another thing?
Who decides? Or is there a way to determine logically? If someone decides, should this be on some official list on the state where this someone has authority?
Maths is supposed to be about logic. If someone decides that squares are rectangles (that is defines the words to be that way) rather than that there is some logical way to deduce such, then these all seem so arbitrary. I think it's similar to how English says 'The plants are tall' not 'The plants is tall' whereas in French or Spanish, I think, the linking verb may contain an 's' if the noun would contain an 's'.
Why isn't there a term for equilateral triangle but there is a term for equilateral rectangle?
Why does the word rectangle exist? Why don't we just use oblong? Is this an English thing? Or a maths thing? Or what?