Material dirt or filth is called “najasah”. Unclean, dirty matter is called “najis”. Taharah from najasah means cleaning the dirty matter regarded as najis on the body or the clothes.

Some of the dirty matter is essentially dirty. Some of them are essentially clean but they become dirty due to being polluted afterwards. An example for the former is urine; and an example for the latter is a clothing item polluted by urine. Urine is essentially dirty. The clothing item was clean but it became najis because it was polluted by urine.