Interesting Math Stuff #4: The Origin of the X

X is the letter most commonly used to represent a variable. X also stands for the horizontal axis in a 2D graph and the first number in an ordered pair. 

During Islamic times, Arabic was the predominant language of sciences. In Arabic the word for thing or object is "shei". Translated into Greek is xei, which is then shortened to x. also, the word "xenos" is the greek word for unknown or stranger, so this could also be a reason that we use x for the unknown variable in math. 

Source: http://www.newton.dep.anl.gov/askasci/math99/math99228.htm

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