A monomial is an expression with one term. However, the term can not have a variable in its denominator.
A binomial is a polynomial with two terms.
|6x + 3|
|-12x - 3y, 7xy + z|
A trinomial is a polynomial with three terms.
|6x2 + 3x + 5|
|-2xy + 3x - 5z|
The degree of a monomial is the sum of the exponents of its variables.
|-5 has degree = 0 (because it has no variables)|
|6x2 has degree = 2|
|6x2y has degree = 3 (because the exponent on y is 1, we just don't write it)|
The degree of a polynomial is the highest degree of any of its terms, after it has been simplified. (i.e. like terms have been combined)
|6x2 + 3x + 5 has degree = 2 (because 6x2 has the highest degree)|
|-5x + 6x2y + 7x -6x2y + 5xy simplifies to -5x + 7x + 5xy so the polynomial has degree = 2 (because the degree of 5xy is 2)|