Corresponding particles
Antiparticles match their corresponding particles in mass while reversing certain quantum numbers, including electric charge for charged partners. Positrons correspond to electrons and antiprotons to protons. Electrical neutrality alone does not establish that a particle is its own antiparticle; other properties and experimental evidence matter.
Anti-atoms and ordinary physical rules
An antiproton and positron can form antihydrogen, demonstrating a composite antimatter system. Anti-atoms are not ordinary atoms assigned negative mass. Spectroscopic and other precision comparisons test predicted relationships with matter rather than assume that every physical rule must operate in reverse.
Annihilation and energy accounting
Particles and antiparticles can annihilate into photons or other products while conserving energy and momentum. Initial motion affects the outcome. Artificial production requires energy, and preparation and confinement add further costs, so antimatter is not a source of power obtained without prior energy input.
References: [2]
Investigating the asymmetry
The observed matter–antimatter imbalance motivates studies of decays and other particle properties. Accelerators and precision low-energy experiments address complementary questions. Established antiparticles, laboratory anti-atoms and hypotheses about cosmic history have different evidence requirements; one local measurement does not automatically explain the entire asymmetry.