refractile

Refractile is an adjective describing a material that readily refracts light, causing it to bend and alter the path of illumination. In microscopy and histology, the term is used to indicate that a substance or inclusion stands out because of its optical properties rather than its color alone.

In practical use, refractile material is often seen as bright, shiny, or highly conspicuous under light microscopy, especially when observed with techniques that enhance light interaction such as immersion oil, phase contrast, or polarized light. The degree of refractivity depends on the difference between the material’s refractive index and that of the surrounding medium. Because refractile objects bend light differently from the surrounding tissue, they can appear foreshortened or sparkling and may require additional methods to characterize them.

In pathology and cytology, refractile materials commonly include crystalline or particulate substances such as certain crystals and some foreign bodies or pigment deposits. The term emphasizes the optical appearance rather than a specific chemical identity. It is not a diagnosis in itself but a descriptive observation that can guide further analysis.

Refractility is related to, but distinct from, birefringence, a property observed under polarized light where a material splits a light ray into two rays. Some refractile substances may also be birefringent, but not all birefringent materials are described primarily by refractility.

Etymology derives from the verb refract and the suffix -ile, meaning capable of being refracted.