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diffraction
This term describes the bending of waves when they encounter an obstacle or a slit. It is a phenomenon that proves the wave nature of light, contrasting with the particle theory. It occurs most noticeably when the size of the opening is comparable to the wavelength of the wave. In practical applications, this effect is what allows sound to travel around corners or through doorways even when the source is not in a direct line of sight. It differs from refraction, where a wave changes direction by passing from one medium to another, whereas diffraction happens due to the geometry of the path.
Uncountable when discussing the physical phenomenon of wave physics. Countable when referring to specific observed patterns or instances of the effect in an experiment.