>Is it right that "wanna" means "want to" ?
>And about "gonna", does it mean "going to" ?

Yup.  "gonna" is an accepted "eye dialect" spelling for the
most common American pronunciation of the "(be) going (to)"
future construction, as in "I'm gonna kick some butt".

In standard written English, this would be written "I'm going to kick
some butt", but if it were pronounced like that, as
   /aym gowIng tuw kIk s@m b@t/,
it would most likely be interpreted as a joke.

"gonna" is actually pronounced /g@'n@/, with a "flap n" that has a faint
/t/-echo; the stress is on the first shwa.  It's natural and very common
for auxiliary verbs -- especially modal auxiliary verbs -- and their
contractions to change from their original roots. They're used so
frequently that people fall into habits of dealing with them, especially
if the individual words that originally made up the construction have lost
their individual meanings and now form a fixed phrase.

Pretty much the same story with "wanna"; you could call it the
auxiliary for the desiderative mood, where "gonna" is the
auxiliary for the intentive future, if you want fresh traditional
names for them.  But it's just another auxiliary verb.

Oh, and "oughta" /ot@/ (where /o/ represents the "aw" sound of
"caught", "law", and "Dawn" in Midwestern American), from
"ought to" = "should", is also an accepted eye dialect spelling,
as is "hafta" /haeft@/ for "have to" = "must".

A construction of the same sort is "used to" /yust@/, a frequentative
past imperfect auxiliary, but eye dialect spellings of it differ, no
doubt because of different intuitions about folk phonics. I've seen
"yusta", "usta", and "useta", and occasionally "usedta", but none of
them seem as standard as "wanna" and "gonna".

Eye dialect is largely used to represent speech in narratives, and
often carries the (author's) presumption that the speaker is
illiterate or of a lower class.  It's not at all standard in normal
written English, except occasionally on the net, where we sometimes
want to invoke the conversational rules and milieu of spoken
communication.

*Don't* use these words in any formal writing.  On the other hand,
if the person(s) you're writing for can be trusted not to put you
down for your writing, go right ahead and use them.  And if you're
writing a story and want to represent speech, be aware that the
socioeconomic class of the character speaking (or rather the
reader's perception of that class) is affected by the author's
use of eye dialect.

... and in a later post, on a similar topic:

> As a sideline, has anybody else noticed that in the construction
> 'I have to', people often pronounce 'have' as if it were 'haff'?
> Perhaps this, too, is for emphasis.  I can't think of any other
> situation in which it happens.
> 	' Clean your room!' Do I *haff* to?'

Actually, lots of people have noticed it; it's a standard topic
in ESL classes, because English learners have to learn that the
pronunciation is different from what one might expect.  For example:

   I have to shovel the driveway.   /haeft@/
   I have two shovels in the driveway   /haevtu/
The reason is that this "have to" is a periphrastic modal construction
("periphrastic" means composed of a phrase -- several words -- instead
of just a different inflected version of a single word, e.g Latin
perfect passives are periphrastic because they use an auxiliary), and those
virtually all have special pronunciations.

Examples:

    want to  =  "wanna"  /wan@/ with flap /n/

 (be) going to = "gonna"  /g@n@/ with flap /n/

    ought to =  "oughta" /Ot@/ with flap /t/ = /d/

    used to (no standard eye dialect) = /yust@/ with /t/
     (compare X is used to Verb with X used to Verb)

All of these (except the last, which is a periphrastic imperfect
tense) refer to modals.  Ought to is 'should', have to is 'must',
going to is 'will', and so is want to, in the other sense of 'will'
= 'willing'.  Modals need some kind of paraphrases in English,
since they're defective verbs and can't form past tenses, for instance.

There isn't any way to use 'must' in the past, so we use 'had to' instead.
Also, negatives compound differently with them: 'don't have to' isn't
the same as 'must not', etc. 

All of these honorary modals have peculiarities of pronunciation
that mark them as special, and the devoicing of the final /v/ in
'have to' before the voiceless /t/ is an example of that.

  --------------------------------------------
 -John Lawler                     More grammar
  Linguistics Program   University of Michigan
 "..and, who knows? Maybe the horse will sing."