the

With a comparative or with more and a verb phrase, establishes a correlation with one or more other such comparatives.

“It looks weaker and weaker, the more I think about it.”

With a comparative, and often with for it, indicates a result more like said comparative. This can be negated with none. See none the.

“I'm much the wiser for having had a difficult time like that.”

For each; per.

“valued at half a pound the bushel; paying seven dollars the year interest”