Each type of particle must have a corresponding antiparticle type. The mass of any antiparticle is identical to that of the particle. All the rest of its properties are also closely related, but with the signs of all charges reversed. For example, a proton has a positive electric charge, but an antiproton has a negative electric charge. The existence of antimatter partners for all matter particles is now a well-verified phenomenon, with both partners for hundreds of such pairings observed.
New discoveries lead to new language.
By adding the concept of antimatter as distinct from matter, physicists narrowed the definition of matter to apply to only certain kinds of particles, including, however, all those found in everyday experience. Any pair of matching particle and antiparticle can be produced anytime there is sufficient energy available to provide the necessary mass-energy . Any antimatter we produce in the laboratory soon disappears because it meets up with matching matter particles and annihilates. The observed imbalance between matter and antimatter is a puzzle yet to be explained. So clearly this imbalance is a key property of the world we know.