bohr theory: (physics) a theory of atomic structure that combined Rutherford's model with the quantum theory; electrons orbiting a nucleus can only be in certain stationary energy states and light is emitted when electrons jump from one energy state to another
entity: that which is perceived or known or inferred to have its own distinct existence (living or nonliving)
street urchin: a child who spends most of his time in the streets especially in slum areas