Washing machine

A washing machine comprising:

• a main body;
• a tub inside the main body;
• a drum rotatably disposed in the tub to accommodate laundry, the drum including:
• a circumferential wall,
• a rear concave groove portion at a rear end of the circumferential wall and longitudinally extending in a band shape in a circumferential direction of the drum,
• rear through holes in the rear concave groove portion,
• a front concave groove portion at a front end of the circumferential wall and longitudinally extending in a band shape in the circumferential direction of the drum,
• front through holes in the front concave groove portion,
• a first plurality of protruding ribs protruding from an inner surface of the circumferential wall and longitudinally extending in the circumferential direction of the drum, and a second plurality of protruding ribs protruding from the inner surface of the circumferential wall and longitudinally extending in the circumferential direction of the drum, so that a water flow path is formed between the first plurality of protruding ribs and the second plurality of protruding ribs along the inner surface of the circumferential wall between the front through holes and the rear through holes;
• a sprinkler;
• and
• a circulation pump,
• wherein the tub, the drum, the sprinkler, and the circulation pump are configured so that
• the circulation pump supplies water stored in the tub to the sprinkler,
• the sprinkler spays water suppled to the sprinkler by the circulation pump toward laundry accommodated in the tub, and
• water in the drum flows along the water flow path to the rear through holes to be discharged through the rear through holes to the tub, to be stored in the tub.