Matter is defined as anything that has mass and occupies space. Scientifically, it is composed of particles, which are generally understood to be atoms, and these atoms combine to form elements and compounds. Matter exists in several states, most commonly solid, liquid, gas, and plasma, each characterized by distinct intermolecular forces and particle arrangements. The fundamental properties of matter, such as density, volume, and mass, can be quantified and studied to understand the composition and behavior of all physical substances within the known universe.