Both terms are frequently used as same condition. Both conditions are related to coronary artery diseases.
Arteriosclerosis: It is the condition of thickening, hardening, and loss of elasticity of the walls of the arteries.
Atherosclerosis : It is an artery wall thickness (hardening ), and caused by plaque building up in the vessel. Plaque causes thickening of the walls of the artery. Stiffness and a loss of elasticity also the result.