YARFMO (Yet another reposting from Mathoverflow) ;-)

The more you know about math the more you find conceptions previously thought correct to be false:

1.) math is not as exact as many believe - in many cases, as Gowers points out in his amazing book "Mathematics. A very short intro", it is mainly about approximations, boundaries or even "only" existence. Example: The Riemann hypothesis.

2.) math is not "true" (whatever that means) in its own right - it is only true within an axiomatic system (deductive approach). Example: The parallel axiom.

3.) closed form solutions are not as closed as many think: "closed-form" is just shorthand for "popular enough to be given a name and notation." Examples: $\pi, e, \mathrm{Si}(x), \mathrm{li}(x)$.

**My question**

Do you have further common misconceptions about math (ideally also with examples)?

I think that the ones given above only scratch the surface because in the end the picture of math also changes historically the further we proceed on this never-ending endeavor of human mind.

(As should be clear already, I am talking about the "meta'-level, so please don't give examples like $(x+y)^2=x^2+y^2$ - this is already covered here and here.)