Washing machine

A washing machine comprising:

• a casing;
• a washing tub disposed in the casing;
• a drum that is rotatably disposed in the washing tub and that has an elongated cylindrical shape, the drum having an opening defined at a front end of the drum and configured to receive laundry;
• a rear cover coupled to a rear end of the drum;
• a motor configured to rotate the drum, the motor having a rotating shaft that is connected to the rear cover;
• and
• a plurality of lifters that protrude from an inner circumferential surface of the drum and that are formed integrally with the drum, the plurality of lifters extending along a longitudinal direction of the drum,
• wherein the plurality of lifters include:
• a front lifter that is disposed closer to the opening than to the rear cover, and
• a rear lifter that is disposed closer to the rear cover than to the opening and that is spaced apart from the front lifter,
• wherein each of the front and rear lifters includes a front end, a rear end, and side ends connecting the front end and the rear end, and
• wherein the drum defines a reinforcement groove between the front lifter and the rear lifter, the reinforcement groove extending from a first position corresponding to an outer edge of the front lifter to a second position corresponding to an outer edge of the rear lifter through an area between the front lifter and the rear lifter.