The degree (power) of each term in an algebraic expression is the same.

The number of unknowns (called powers) of each term in the equation is the same.

For example:

A 2+B 2+C 2 homogeneous algebraic expression: the degree of each term is: 2 (square term)

AX+by+cz = 0 linear homogeneous algebraic equation (first degree)

F'+2f'+f = 0 second-order linear (first-order) homogeneous ordinary differential equation

Wait, it's all homogeneous. The 0 at the right end of the equal sign is also an item: 0 multiplied by any item or 0 does not affect homogeneity.