The Greek letter Kappa (κ) is sometimes used in math. For example, in differential geometry, the curvature of a curve is given by κ.
Frequency.
y-axis
kilometers
Hypotenuse, hexagon
universal graph, uranium, umbra
Geometry
vector
hypotenuse
linear
Quadratic, quotient.
integers?
hypotenuse, hexagon, half, hectometre, hectogram (etc), Hamiltonian, hyperbola, hyperbolic, hypergeometric are some.