x1 is emitted/reflected light that measures to be x2 magnitudes in luminous brightness, on scale (si'o)/using reference value/under system/according to definition x3, in logarithmic base x4 (default: decimal (10))
Wavelength is specified in x1; it is improper to submit an object as the sumti for x1. The type of magnitude (absolute, apparent, etc.) must be specified by tanru or lujvo. x2 must be a pure number (dimensionless). The system/scale being used (x3) must specify the reference emission and its reference value/magnitude (for example: the brightness of Vega measures to be 0 magnitudes in all wavelengths), the unit (the meaning of a change by 1 magnitude), and the direction of increasing brightness (traditionally: lesser magnitudes represent increased brightness); note that magnitude is defined for all real numbers. See also: gu'irnilcarmrmagnitu.