There’s no real definition for the word "to" because it's a word that primarily just serves a function … 22 of them, actually. Yup, there are 22 uses for the preposition “to.” MORE VIDEOS FROM DICTIONARY.COM
To vs. Too. Too is an adverb that can mean “excessively” or “also.” Just to be clear: two is pronounced the same as to and too, but it can’t be used instead of either of them because it’s a number. In the hierarchy of things that drive grammar sticklers mad, to and too are near the top.
Too means also (I’m going, too) or to an excessive degree (too much). Two is the number equal to one plus one. The words are used in very different ways: to is most commonly used as a preposition, too is an adverb, and two is a number that can be used as a noun or an adjective.
Word Origin and History for too. The spelling with -oo is first recorded 1590. Use after a verb, for emphasis (e.g. did, too! ) is attested from 1914. German zu unites the senses of English to and too . Slang too-too "excessive in social elegance" first recorded 1881. Too much "excellent" first recorded 1937 in jazz slang.