Washing machine

A washing machine, or washer, is a machine designed to wash laundry, such as clothing, towels and sheets. The term is mostly applied only to machines that use water as the primary cleaning solution, as opposed to dry cleaning (which uses alternative cleaning fluids, and is performed by specialist businesses) or even ultrasonic cleaners.
All washer machines work by using mechanical energy, thermal energy, and chemical action. Mechanical energy is imparted to the clothes load by the rotation of the agitator in top loaders, or by the tumbling action of the drum in front loaders. Thermal energy is supplied by the temperature of the wash bath.
Clothing had been hand-washed for thousands of years, by flushing water through the fabric to remove loose dirt, rubbing with soap to remove oils and stains, and applying fragrances to cover odors. For particularly dirty clothing covered with mud or dirt, it was necessary to constantly rub and flex the cloth to break apart solids and help the soap penetrate through thick, dry, or sticky layers of soil on the cloth.
At first this was done by pounding or rubbing the clothing with rocks in a river, and later developed into the corrugated wash board. In Roman times a fuller would whiten clothing by stomping on it in a bucket full of fermented urine.