A trinomial is a type of polynomial that consists of three terms. These terms are usually separated by addition or subtraction signs. For example, the expression x^2 + 5x + 6 is a trinomial because it has three distinct parts: x^2, 5x, and 6. Trinomials can represent various mathematical relationships and are often used in algebra. Trinomials can be classified based on their degree, which is determined by the highest exponent of the variable. The most common form of a trinomial is a quadratic trinomial, where the highest degree is 2, such as ax^2 + bx + c. These expressions can be factored or solved using various algebraic methods.