Why is defined as for what purpose, cause or reason.(adverb)
An example of why is when it is used to ask a question such as "Why are you drinking water?
See why in Webster's New World College Dictionary
Origin: ME hwi < OE, instrumental case of hwæt, what
noun pl. whys
See why in American Heritage Dictionary 4
Origin: Middle English
Origin: , from Old English hwȳ; see kwo- in Indo-European roots. Usage Note: Many critics have held that why is redundant in the expression the reason why, as in The reason why he accepted the nomination is not clear. While it is true that why could be eliminated from such examples with no loss to the sense, the construction has been used by reputable English writers since the Renaissance. See Usage Note at where.
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