The Oxford English Dictionary, or OED, has many definitions for the word light as it in itself is a very complex concept. First uses of the word Light have been traced back as early as 1000 B.C.E. The Oxford English Dictionary defines Light in a general sense as “that natural agent or influence which (emanating from the sun, bodies intensely heated or burning sources) evokes the functional activity of the organ of sight” (OED) Light finds its roots in various Proto-Indo-European words such as: bhāos, leghús, and leuks. Leuks is also the proto-ido-european root for looks. Light later developed into the Sanskrit root ruc, to shine, and rṓcas and rōcís, brightness. The first use of the word light as we understand it was in the Old English-Middle English version around 1000 B.C.E as leoht. The spelling of light as we see it today was actually used by William Shakespeare in a narrative poem in 1594 (OED). Since then, the word light has been adopted into many fields with an ever growing understanding of the word.
The OED provides subsequent definitions for light, but light is always best understood when compared with darkness. Light is defined as a influence that allows us to see, but if everything were to be illuminated then there would be no way of differentiating light from darkness; and the same were to be true if everything were only darkness. It is from this curiosity with defining light that many scientific fields have emerged in the study of light and its properties.
The first use of light in a scientific application was by Sir Isaac Newton in the year 1704 on the topic of Opticks or optics. The study of geometric optics is the study of how light travels in a straight line and what happens to it when refracted or reflected. This study of light becomes a larger study of what light is in a physics sense. Physicists such as Thomas Young, Albert Einstein, and Max Planck have tried to define light and its properties as it exhibits both wave properties and particle properties. The study of light can also be applied in a chemistry application in the wave spectra of electrons and their valence shells.
The study and application of light as we know it is a vast field that most people still do not understand today. By defining the word we come closer to a better understanding of what light is, and we may never really be able to fully understand what light is; it may be one subject that will fascinate us for years to come.
"light, n.1". OED Online. September 2012. Oxford University Press. http://www.oed.com/view/Entry/108172?rskey=M7umM4&result=1&isAdvanced=false (accessed November 21, 2012).