To

Preposition

Destination marker

If there is one sign that symbolizes the word "to" it is an arrow. ( ⇒ )

• I'm going to the store
• Give it to your brother.
• Happy birthday to you!

• She's going to China. -- Je vais en Chine (f.) // au Japon. (m.)
• Welcome to France. -- Bienvenue en France (f.) // au Japon. (m.)

The most famous line from Shakespeare's Hamlet can also be understood in this light:

• To be or not to be: that is the question?

For Hamlet at this moment of the play, "being" is a still a destination, or an objective that is not fully realized.

Directional marker: towards

• toward, towards = vers, en direction de
  • He was moving towards the door. He obviously wanted to leave.
    
  • The two countries were headed towards war.
  • "Chesapeake Energy (NYSE:CHK) is likely headed towards bankruptcy. Don’t be fooled about this. CHK stock will then be worthless if that occurs." §§

Combines with "in" and "on"

• into: (inchoative particle: marks a beginning) marque le point où un "intérieur" commence à être franchi
  • come into / go into / run into (STH) (car accident) / run into (SO) (croiser qqn)
  • turn into, change into = (se) transformer en
  • change into warmer clothes = aller mettre, aller enfiler
  • look into, delve into = étudier de plus près
  • talk so into sth = convaincre qqn de faire qqch.
• onto:
  • The destination physically supports (or holds up) the "subject" of the sentence, keeps it from falling.
    • Should we move the computer onto the desk?
    • There's no way you're going to be able to put the iPad onto your unlimited plan with verzion.
• be on to:
  • vient du sens continuatif de on, notion de découverte d'une bonne piste...
    • I think you're on to something here.
• up to:
  • upper limit
    • Everything must go! Up to 70% off!
    • In the Sahara, the temperatures get up to 110° during the day and down to 50° at night.
  • doing
    • What are you up to these days?

Infinitivals

Combines with any number of verbs to introduce a complement or a predicate :

• She wants [to get some new shoes].
• "When purchasing life insurance, there are a few specific questions that you're not going [to want [to forget [to ask __???____ ]]]]."
• They don't know how [to operate the machine yet]. They need [to be trained].

phonetic reduction

There are two principle verbs where the [t] loses its "obstruent" nature in rapid speech. (It loses it's "T-ness" if you like):

• want to    →    wanna'
• going to    →    gonna'

modality of "to"

Modality#Modality_of_to