You can also discuss how a polynomial of degree $n$ can be defined in two different ways – either as the $n+1$ coefficients of powers of $x$, or the values of the polynomial at $n+1$ distinct inputs. In linear algebra terminology, such polynomials belong to an $n+1$-dimensional vector space. A more intuitive notion of dimension that may be more suitable at this level is a measure of "free"-ness: add a dimension for each (real-valued) free variable and subtract one for each constraint.