Non-SI unit of @P04686@, \(1\ ^{\unicode{x26ac}} = \frac{\pi }{180}\ \text{rad}\approx 0.017\ 453\ 29\,...\,\text{rad}\).
Sources: Green Book, 2nd ed., p. 113 [Terms] [Book] PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 968 [Terms] [Paper]