degree

https://dx.doi.org/10.1351/goldbook.D01560
Non-SI unit of plane angle, 1 ° = π 180 rad ≈ 0.017 453 29 ... rad.
Source:
PAC, 1996, 68, 957 (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 968