It is defined **monomial** as a literal algebraic expression, consisting of a numerical part (coefficient) and a literal part among which only multiplication and exponentiation operations appear; for example:

\[\dfrac{1}{2}x;\;7x^2y;\;-9x^n\]

The monomial degree is defined as the sum of all the exponents of the literal part. Monomes that have the same literal part (with identical exponent) are said to be similar, and among these, only algebraic operations of sum and difference are allowed; on the other hand, multiplication and division operations are always allowed even between monomials whose exponents of the literal part are not equal (but always having the same literal part).