Arteriosclerosis and atherosclerosis are sometimes used to mean the same thing, but there's a difference between the two terms.
Arteriosclerosis occurs when the blood vessels that carry oxygen and nutrients from the heart to the rest of the body (arteries) become thick and stiff — sometimes restricting blood flow to the organs and tissues. Healthy arteries are flexible and elastic. But over time, the walls in the arteries can harden, a condition commonly called hardening of the arteries.
Atherosclerosis is a specific type of arteriosclerosis.
Atherosclerosis is the buildup of fats, cholesterol and other substances in and on the artery walls. This buildup is called plaque. The plaque can cause arteries to narrow, blocking blood flow. The plaque can also burst, leading to a blood clot.