the

Etymology 1

From Middle English the, thy, thi, from Old English þē̆, probably a neuter instrumental form ("by that, thereby")—alongside the more common þȳ and þon—of the demonstrative pronoun sē ("that"). Compare Dutch des te ("the, the more"), German desto ("the, all the more"), Norwegian fordi ("because"), Icelandic því (“the; because”), Faroese tí, Swedish ty.

adv

1. With a comparative or with more and a verb phrase, establishes a correlation with one or more other such comparatives.
   The hotter(,) the better. (comma usually omitted in such very short expressions)
   The more I think about it, the weaker it looks.
   The more money donated, the more books purchased, and the more happy children.
   It looks weaker and weaker, the more I think about it.
2. With a comparative, and often with for it, indicates a result more like said comparative. This can be negated with none.
   It was a difficult time, but I’m the wiser for it.
   It was a difficult time, and I’m {none - not any} the wiser for it.
   I'm much the wiser for having had a difficult time like that.

Etymology 2

prep

1. For each; per.
   valued at half a pound the bushel; paying seven dollars the year interest
   Next morning I was up at an early hour, to see the market held near the water gate. The beef was excellent: but at the high prices of ten-pence and one shilling the pound; mutton at the same price; fowls a dollar the couple, and showing “more feathers than flesh.” 1837, James Edward Alexander, Narrative of a Voyage of Observation Among the Colonies of Western Africa, in the Flag-ship Thalia; and of a Campaign in Kaffir-land, on the Staff of the Commander-in-Chief, in 1835, volume 1, London: Henry Colburn, pages 251–2