Condensation between two molecules of an aldehyde or a ketone having atleast one $\alpha$-hydrogen atom in presence of a base to form a $\beta$-hydroxy aldehyde or $\beta$-hydroxy ketone is known as aldol condensation. Aldol condensation are divided into two parts one is self aldol condensation and another is cross-aldol condensation, when both molecules are same called self aldol and vice versa.