Generally speaking, equations with unknowns are called equations. We can classify them from different angles.

From the index of unknown quantity, it can be divided into linear equation, quadratic equation, cubic equation and ... n-degree equation.

From the number of unknowns, it can be divided into one-dimensional equation, two-dimensional equation, three-dimensional equation and ... n-dimensional equation.

From the classification of algebraic expressions: fractional equation, fractional equation, radical equation and so on.