Wudu is the Arabic name for the pre-prayer washing ritual required before many acts of Islamic worship.
The ritual normally involves washing the hands, mouth, nose, face, arms, head, and feet in a prescribed sequence. It symbolizes physical cleanliness and readiness for worship. Muslims generally perform it before salah when the previous state of ritual purity has been broken.
Wudu is not the same as ghusl, the full-body purification required in circumstances such as major ritual impurity. When water is unavailable or harmful to use, Islamic law provides tayammum, a dry purification using clean earth or a similar natural surface. Details of the sequence and what invalidates wudu can vary among schools of Islamic jurisprudence.