Mass is a fundamental physical measure that quantifies the amount of matter in an object, representing its resistance to changes in motion. It is a scalar quantity, distinct from weight, which is a vector quantity influenced by gravity. The standard unit of mass in the International System of Units (SI) is the kilogram (kg), though grams (g) and other units like pounds and ounces are also commonly used in various contexts. Mass plays a crucial role in both everyday life and scientific research, as it affects an object's inertia, gravitational pull, and energy content, according to Einstein's famous equation, E=mc². Understanding mass is essential in fields such as physics, chemistry, engineering, and astronomy, where it helps in analyzing the behavior of objects, materials, and celestial bodies, making it a cornerstone of modern science and technology.