Through is defined as in at one side or end and out at another.(preposition)
An example of through is a train traveling the distance of a tunnel.
Through means completely or to the end.(adverb)
An example of through is to see a plan all the way from its conception to its execution.
See through in Webster's New World College Dictionary
Origin: ME thurgh, thrugh < OE thurh, akin to Ger durch < IE base *ter-, through, beyond > L trans, across, Sans tiráḥ, through
See through in American Heritage Dictionary 4
Origin: Middle English thurh, through
Origin: , from Old English thurh; see terə-2 in Indo-European roots.
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