Ich würde schreiben: "nth-degree polynomial"

PS. Die Anfrage wäre in der Kategorie "proposed translation correct?" oder "English missing" besser aufgehoben gewesen.

Of course, if n = 1, then it's "nst" grade, if 2, then "nnd grade", if 3, then "nrd grade". Otherwise, "nth grade".
Just kidding.

of degree n (keinesfalls grade!)

I know that for exapmple: x hoch 2: x squared , x hoch 3: x cubed, and every n bigger than that: x hoch n:x to the nth power.
But if u have an entire funktion, you call highest power "degree"(or "order"). For example: An entire function of 2nd degree(order) is called a quadratic function; an entire function of 4th degree(order) is called an biquadratic function ...