| Word | Definitions | Synonyms |
|---|---|---|
| birefringence | (noun) splitting a ray into two parallel rays polarized perpendicularly | Synonyms: double refraction |
| birefringent | (adjective) relating to or characterized by double refraction | - |
| biretta | (noun) a stiff cap with ridges across the crown; worn by Roman Catholic clergy | Synonyms: berretta, birretta |