Pronunciation: [lˈuːmɛn] (IPA) 
The word "lumen" is spelled with four letters, but its pronunciation is not immediately obvious. In IPA phonetic transcription, it is pronounced /ˈluːmən/ (LOO-mun), with the stress on the first syllable. The "u" sound is long, as in "cue," and the "e" is pronounced like a schwa sound, as in "the." The word refers to the unit used to measure the amount of light emitted by a source, often used in the context of lighting fixtures.
A lumen, in general terms, refers to the standard unit of measurement for luminous flux, which quantifies the total quantity of visible light emitted by a source in all directions. It is utilized to assess the brightness or intensity of light perceived by the human eye. The lumen value symbolizes the total amount of light energy radiated per second in a specific direction by a light source. This unit's definition is essential for accurately gauging the light output or intensity of various lighting fixtures, including light bulbs, lamps, and other lighting devices.
The lumen is slightly different from the unit of measurement known as the candela, which quantifies the luminous intensity produced by a light source within a specific solid angle. The lumen represents the overall quantity of light energy emitted by a light source, irrespective of its directionality, whereas the candela accounts for the intensity of the light within a specific cone-shaped region.
The lumen is utilized to compare and assess the brightness or luminosity of various light sources. This measurement is significantly helpful for individuals when choosing lighting products for their specific needs, ensuring they acquire lamps or bulbs that generate adequate illumination for their intended application. Additionally, the lumen value enables consumers to make informed decisions regarding the energy efficiency of different lighting options, allowing them to select lighting fixtures that provide optimal brightness while consuming less power. Overall, the lumen is an integral unit of measurement for accurately evaluating and comparing the brightness and luminous output of light sources.
The space in the interior of a tubular structure, such as an artery or the intestine.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.
The word "lumen" originated from Latin. It comes from the noun "lūmen", which means "light" or "radiance". The Latin word also has roots in the verb "lūcere", which means "to shine". The term "lumen" is now commonly used in scientific contexts to specifically refer to the unit of measurement for luminous flux, which is the total amount of visible light emitted by a source per unit of time.
