Applied Physics and Mathematics Annotation << Back PHYSICAL CATEGORIES – MASS AND DENSITY OF BODIES F.F. GORBATSEVICH Mass is a fundamental physical quantity that determines the inertial and gravitational properties of bodies from macroscopic objects to atoms and elementary particles. According to the completed study, body mass is the sum of the volumes of atomic nuclei contained in the body. The measure of density is the ratio of the nucleus volume of an element to the volume occupied by an atom in space. The proposed measure of mass and density is true for any physical body on any space object. Keywords: atom;body; density; element; mass; nucleus; volume. DOI: 10.25791/pfim.03.2023.1258 Pp. 14-23.