A quartic equation is a type of polynomial equation that involves terms of degree four. It can also be referred to as a fourth-degree equation, since it has the highest degree of a four-term polynomial. Other synonyms for quartic equation include biquadratic equation, tetradic equation, or quartical equation. Quartic equations can be solved algebraically using methods such as factoring, completing the square or using the quadratic formula. In addition to their mathematical significance, quartic equations also are relevant in physics when analyzing certain phenomena like oscillations, vibrational modes of molecules, and the motion of objects under the influence of gravity.