Non-SI unit of plane angle. \[1^{\prime} = (1/60)^{\,\unicode{x26ac}} = 2.908\ 882\,...\,\times 10^{-4}\text{rad}\]
Sources:
Green Book, 2nd ed., p. 113 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)
PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 981 (https://doi.org/10.1351/pac199668040957)