birefringence
noun
bi·re·frin·gence ˌbī-ri-ˈfrin-jən(t)s 
plural birefringences
1
: the refraction of light in an anisotropic material (such as calcite) in two slightly different directions to form two rays
According to G. Blom of Philips, video disc acrylics must be optically clear and free of striations and birefringence. Clear vinyl often is highly birefringent. 
Technical Survey
Technical Surveycalled also double refraction
2
: the visual effect produced by birefringence
The diagnosis was made before scanning in 22 patients by the detection of deposits with apple-green birefringence … Philip N. Hawkins et al.
Philip N. Hawkins et al.3
: the difference between the angles of refraction of light rays exhibiting birefringence
birefringent
ˌbī-ri-ˈfrin-jənt
adjective 
Example Sentences
Recent Examples on the Web Like ordinary cellophane, the birefringence can split light into separate directions, leading to weird optical illusions, distortions, and magnification—all from the simple presence of the magnetic field. Paul Sutter, Ars Technica, 17 June 2022 This produces something called a birefringence in the vacuum itself. Paul Sutter, Ars Technica, 17 June 2022 One of them is known as vacuum birefringence: the notion that a strong, external field can cause this type of polarization — the creation of an internal field — to empty space itself. Ethan Siegel, Forbes, 7 May 2021
Paul Sutter, Ars Technica, 17 June 2022 This produces something called a birefringence in the vacuum itself. Paul Sutter, Ars Technica, 17 June 2022 One of them is known as vacuum birefringence: the notion that a strong, external field can cause this type of polarization — the creation of an internal field — to empty space itself. Ethan Siegel, Forbes, 7 May 2021 Word History
Etymology
International Scientific Vocabulary bi- entry 1 + refringent refracting, from Latin refringent-, refringens, present participle of refringere to break up — more at refract
First Known Use
1879, in the meaning defined at sense 1
Medical Definition
birefringence
noun
bi·re·frin·gence ˌbī-ri-ˈfrin-jən(t)s
: the refraction of light in an anisotropic material in two slightly different directions to form two rays
also : the visual effect produced by birefringence
The diagnosis was made before scanning in 22 patients by the detection of deposits with apple-green birefringence … Philip N. Hawkins et al., The New England Journal of Medicine
Philip N. Hawkins et al., The New England Journal of Medicine