Nonreciprocal directional dichroism in multiferroics,namely magnetoelectric coupling in the dynamic regime,is endowed with rich physics and promising applications,which are entangled with fundamental physical components,such as spin,orbital,lattice,charge,and topology.Such a linear nonreciprocal response behavior in the GHz-THz frequency range,represented by optical magnetoelectric effect and magnetochiral dichroism,occurs ubiquitously in material systems with the spontaneous breaking of space-time symmetry,and is subject to Onsager's reciprocal theorem in the thermodynamic limit.Microscopically,these nonreciprocal responses are usually encoded by toroidization (chirality) and electromagnon (quasiparticle),thus establishing a comprehensive understanding of magnetoelectric coupling and irreversible dynamics.Herein,the basic mechanisms and emergent nonreciprocal directional dichroism in single-phase multiferroics are summarized.We expect that the present review will stimulate diverse possibilities toward nonreciprocal directional dichroism within and beyond multiferroics.