Classify the following polynomial as a polynomial in one variable,two variables,etc.:
$x y + y z + z x$

Write the degree of the following polynomial: $x^{8}-6561$.

For the polynomial $\frac{x^{3}+2 x+1}{5}-\frac{7}{2} x^{2}-x^{6},$ write:
$(i)$ the degree of the polynomial
$(ii)$ the coefficient of $x^{3}$
$(iii)$ the coefficient of $x^{6}$
$(iv)$ the constant term

Find the degree of the following polynomial: $x^{3}-3(x^{2})^{4}-15$.

Determine the degree of the following polynomial:
$2x - 1$

Classify the following as a linear,quadratic,or cubic polynomial:
$5 - 3t$