Mass is the measure of the amount of matter present in a body. It represents how much substance or material an object contains, regardless of its shape, size, or position.
Mass is a scalar quantity (it has magnitude but no direction) and remains constant everywhere, unlike weight which changes with gravity. The SI unit of mass is the kilogram (kg).
Example: A stone has the same mass on Earth and on the Moon, but its weight will be less on the Moon due to weaker gravity.