Which expression is not a polynomial?

-+2 is not a Polynomial,This one is a radical term.

Explanation:

A polynomial can own:

That can be joined utilizing the four operations (+,-,*,/)

So: A polynomial can have, variables, constants, and exponents,

but  a variable can divide.

Also, they can have one or more terms, but not an endless number of cycles.

vx is not, because the exponent is "½" (see fractional exponents).