A member of a class of subatomic particles called baryons, which exists in four electric charge states and has a total spin of J = 3/√2. In the underlying quark model, the delta resonance (Δ) consists of three quarks whose intrinsic spins of ½ are lined up in the same direction. The Δ is closely related to the more familiar nucleon constituents of atomic nuclei, the neutrons (n) and protons (p).