cube root	The number which, when multiplied together three times yields the original number. For example, the cube root of 64 is 4 because 4 • 4 • 4 = 64.
index	The small positive integer just outside and above the radical symbol that denotes the root. For example, denotes the cube root.
perfect cube	A number whose cube root is an integer.
principal root	The positive square root of a number, as in . By definition, the radical symbol always means to find the principal root. Note that zero has only one square root, itself (since 0 • 0 = 0).
radical expression	An expression that contains a radical.