Quick
Mass is the quantity of matter that an object contains. The SI unit of mass is the kilogram abbreviated kg. The US customary unit is pound mass, abbreviated lbm or lbm.
Details
Mass is the quantity of matter that an object contains. Many times mass and weight are confused. Weight depends both on the quantity of matter in an object and on the force of gravity on the object. An astronaut on the moon weighs only one-sixth as much as the astronaut weighs on Earth. The mass of the astronaut is the same on the moon as on Earth.
Mass is measured by comparing the weights of unknown objects with the weights of known masses by means of a balance. Because both sides of the balance are the same distance from the center of the Earth, the force of gravity on them is the same. When the two sides balance, the masses on the pans must be equal. The known masses are calibrated by comparison with standard masses.
Mass is a quantitative measure of inertia. The greater its mass, the more a body "resists" being accelerated. The same force creates a larger acceleration on a smaller body than on a larger one.
The SI unit of mass is the kilogram.
Related
▪ L - Mass, English System of Units