wavelength, \(\lambda\)

Distance in the direction of propagation of a periodic wave between two successive points where at a given time the phase is the same.
Green Book, 2nd ed., p. 30 (https://dev.goldbook.iupac.org/files/pdf/green_book_2ed.pdf)
ISO 31-05: 1992 (http://www.iso.org/iso/catalogue_detail.htm?csnumber=3635)
PAC, 1996, 68, 957. 'Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)' on page 998 (https://doi.org/10.1351/pac199668040957)
See also:
PAC, 1985, 57, 105. 'Names, symbols, definitions and units of quantities in optical spectroscopy (Recommendations 1984)' on page 109 (https://doi.org/10.1351/pac198557010105)
PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2283 (https://doi.org/10.1351/pac199668122223)