Too
Too is an adverb, and two different meanings give it two different distinct placements.
Too meaning excessively, to an excessive degree
* You worry too much.
* Isn't it just too obvious?
In these cases, the adverb too precedes an adjective.
Too meaning also, in addition
* Zelda is coming too.
* Don't forget to buy red onions too.
To
The confusion about to and too comes from two obvious facts: the words look very much alike, the only difference being that too has one more o than to, and they sound exactly alike. Their distinct origins - to comes from Old English, while too had an extra step in Middle English - is just not salient and memorable for most people to remember.
It's their meanings and use in sentences that set them apart. So let's focus on the meaning aspect.
To is a particle. The infinitive in English consists of two parts: the particle to and the verb. Here are four infinitives:
to giggle, to chuckle, to snigger, to laugh
If you see to before a verb, as above, it's acting as part of the infinitive. Too never does that.
* Gretchen snickered when Hannah said she wanted to order fish and chips.
* To climb Mount Everest takes guts.
To used as a particle and too used to modify a following adjective can look deceptively similar:
* Edna went to work.
* Charles arrived too late.
You may have to actually stop and think: to before a verb or a prepositional phrase; too before an adjective to keep them separate in your mind.
To is a preposition. Definitions of preposition are not very clear, which might be one reason why it's hard to distinguish to and too. The definitions of prepositions say things like ?connects a substantive with a verb, adjective or other substantive.? It?s really hard to tell what that means.
Usually people just learn a group of standard prepositions, like:
above
about
after
around
at
before
behind
beside
beyond
for
from
in
near
of
off
on
over
past
through
under
until
upon
with
without
And remember that they introduce prepositional phrases. Prepositional phrases can be either adjectival or adverbial phrase. Simply put, they can either modify nouns:
* the lady with the forty-two orange scarves (?with the forty-two orange scarves? tells which lady)
Or they can modify verbs:
* was running through the spiky thorn bushes (?through the spiky thorn bushes? tells where the running was taking place).
It's fairly easy to identify to as a preposition in sentences that have prepositional phrases.
* Ernesto skateboarded to the gym
* Pauline spoke to her teacher.
To is an anaphor. Sorry! Anaphor is not commonly taught, but it?s an important use of to and one that's often confused with too, because it can come at the end of a sentence. An anaphor is simply a word that stands in for another word or group of words.
There is one type of anaphor that you?ve probably heard of: pronoun. A pronoun stands in for a noun or noun phrase. Well, pronoun is a member of the anaphor group. Yes, group: there are other words that can act as anaphors, and the particle to is one of them. Here?s how it works:
First a phrase beginning with an infinitive appears, say:
* to get up early and catch the bus to the fish market
Then, there?s a reference back to it in which to stands for the entire phrase so it doesn?t all have to be repeated. In these cases, to usually ends the sentence.
* Gillian plans to get up early and catch the bus to the fish market, but I certainly don?t plan to.
THIS IS NOT A DANGLING PREPOSITION! It can?t be, because it?s not a prepositional use of to!
But, because the to comes at the end of the sentence, where we are used to seeing too meaning ?in addition,? we may unthinkingly substitute one for the other.
