In physics, the name for something that is considered to be both a wave and a particle is "wave-particle duality." This concept refers to the observation that certain entities, such as photons (particles of light) and electrons, can exhibit properties of both particles and waves, depending on how they are observed or measured.
According to wave-particle duality, particles like electrons and photons can exhibit particle-like behavior in some experiments, where they behave as discrete, localized entities with definite positions. In other experiments, they can exhibit wave-like behavior, such as interference and diffraction patterns, which are characteristic of waves.
This duality was initially discovered in experiments studying the behavior of light, where it was found to exhibit wave-like properties, such as interference and diffraction, as well as particle-like properties, like the photoelectric effect. The wave-particle duality concept was further extended to other particles, leading to the development of quantum mechanics, which describes the behavior of microscopic entities at the quantum level.