Detergent is a substance that's used for cleaning. Detergent is similar to soap, but it's stronger and dissolves more completely in water.
Detergents are special, powerful cleansers that can break up dirt, oils, and grease in clothing or on dishes. You might buy laundry detergent for washing your dirty clothes and dish detergent for the sink full of plates and bowls after your dinner party. The Latin root of detergent is detergere, "to wipe away or cleanse."