A quotation by Étienne-Louis Malus


We find that light acquires properties which are relative only to the sides of the ray, -- which are the same for the north and south sides of the ray, (using the points of the compass for description's sake only) and which are different when we go from the north and south to the east or to the west sides of the ray. I shall give the name of poles to these sides of the ray, and shall call polarization the modification which gives to light these properties relative to these poles.