The Definition

thē before a vowel; thə before a consonant

article

Used before singular or plural nouns and noun phrases that denote particular, specified persons or things.

The baby; the dress I wore.

American Heritage

Used before a noun, and generally stressed, to emphasize one of a group or type as the most outstanding or prominent.

Considered Wicker Park to be the neighborhood to live in these days.

American Heritage

Used to indicate uniqueness.

The Prince of Wales; the moon.

American Heritage

Used before nouns that designate natural phenomena or points of the compass.

The weather; a wind from the south.

American Heritage

Used as the equivalent of a possessive adjective before names of some parts of the body.

Grab him by the neck; an infection of the hand.

American Heritage

adverb

That much; to that extent.

The better to see you with.

Webster's New World

By how much . . . by that much; to what extent . . . to that extent.

The sooner the better.

Webster's New World

Beyond any other.

Enjoyed reading the most.

American Heritage

adjective

That (one) being spoken of or already mentioned.

The story ended.

Webster's New World

That (one) which is present, close, nearby, etc., as distinguished from all others viewed as remote.

The day is starting out warm; the heat is oppressive.

Webster's New World

That (one) designated or identified, as by a title.

The President (of the U.S.), the Mississippi (River)

Webster's New World

That (one) considered outstanding, most fashionable, etc.

That's the restaurant in town.

Webster's New World

That (one) belonging to a person previously mentioned or understood.

Take me by the hand; rub into the face.

Webster's New World

preposition

To each; in each; for each; per.

At five dollars the half ton.

Webster's New World

Origin of The

From Middle English, from Old English þē (“the, that", demonstrative pronoun), a late variant of sÄ“ (“that, the"). Originally masculine nominative, in Middle English it superseded all previous Old English forms (sÄ“, sÄ“o, þæt, þā), from Proto-Germanic *sa (“that"), from Proto-Indo-European *só, *to-, *tód (“demonstrative pronoun"). Cognate with West Frisian de, dy (“the, that"), Dutch de, die (“the, that"), Low German de, dat (“the, that"), German der, die, das (“the, that"), Danish den (“the, that"), Swedish den (“the, that"), Icelandic það (“that").

From Wiktionary
From Middle English, from Old English þȳ (“by that, after that, whereby"), originally the instrumental case of the demonstratives sÄ“ (masculine) and þæt (neuter). Cognate with Dutch des te ("the, the more"), German desto ("the, all the more"), Norwegian fordi ("because"), Icelandic því (“because").

From Wiktionary
Middle English from Old English alteration (influenced by th- oblique case stem of demonstrative pron.) of se masculine demonstrative pron. so- in Indo-European roots

From American Heritage Dictionary of the English Language, 5th Edition
Middle English from Old English thȳ, thē instrumental of thæt neuter demonstrative pron. to- in Indo-European roots

From American Heritage Dictionary of the English Language, 5th Edition