Is there any difference between "you are going to love it " and "you gonna love it"?
You're gonna get yourself in trouble
To head off suggestions that these words are more than synonymous, but identical, let me cite the OED [paywalled] here:
Pronunciation: Brit. /ɡənə/, /ˈɡɒnə/, U.S. /ɡənə/, /ˈɡɔnə/, /ˈɡɑnə/
Forms: regional and colloq. (orig. U.S. regional), gona, gonna; Eng. regional...
Frequency (in current use): *****--- (5/8)
Origin: A̲ ̲v̲a̲r̲i̲a̲n̲t̲ ̲o̲r̲ ̲a̲l̲t̲e̲r̲a̲t̲i̲o̲n̲ ̲o̲f̲ ̲a̲n̲o̲t̲h̲e̲r̲ ̲l̲e̲x̲i̲c̲a̲l̲ ̲i̲t̲e̲m̲. Etymon: English going to.
Etymology: Representing a regional and colloquial pronunciation of going to (see go v.), with reduction of the unstressed vowel and assimilatory loss of the initial consonant of the second element.
With auxiliary be: going to (see go v. 51a(a)).
As a simple modal auxiliary, followed by the bare infinitive.
a. Used to express a plan or intention, or to make a prediction. (a) Am (or is, etc.) going to (see go v. 51a(b)).
... [more definitions follow]
So going to and gonna are two separate words (well, lexemes) used in different circumstances.
Broadly, one writes "going to" but one says "gonna" (not always, but frequently).
Spoken vs Written language
Thanks to @tchrist in the comments, here is an analysis from our resident linguist, Prof. John Lawler, where he posted a message to the alt.usage.english Usenet group:
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.
[The word] "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 They're used so frequently that people fall into habits of dealing with them, especially if the individual words that originally made up the construction have lost their individual meanings and now form a fixed phrase.
And, later in the same message:
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.
Gonna [is used] to express the going to form of the future is used with first second and third person singular and plural. Note that in the interrogative, are is omitted in second person singular and first and second person plural
That is, you would say "I'm gonna eat a pie [in the future]" instead of "I am going to eat a pie", but you would not say *"I'm gonna store" instead of "I'm going to the store" (but you could say "I'm gonna store the pie in the fridge" or "I'm gonna go to the store"; doncha love English?).
English is gonna change
So why this distinction between spoken gonna and written going to?
In short: English is an analytic language (expresses meaning through arrangement of separate words, aka syntax), but there is a well-established pattern of analytic languages slowly transforming into synthetic languages (expressing meaning through changing individual words, aka morphology):
source: The Grammaticalization Cycle, Prof. John Lawler (undated)
So what you see here, with people pronouncing going to as gonna, are "transitional fossils"¹ of English slowly (~1K years) transforming from analytic to synthetic.
But as writing lags speech, so even where someone would say "gonna" (which is very common, even among the educated²), he would still write "going to".
It will take a long time for conscientious English speakers to actually write
g o n n a in anything but the most informal settings³, or, as Dr. Lawler points out, when imitating colloquial speech intentionally in writing to give a story a more grounded flavor.
¹ Technically, the "transitional fossils" would be exactly when people wrote down words like "gonna". The spoken forms are more like the ephemeral soft tissue in monsters of epochs past. Unrecoverable.
² I know I've seen Dr. Lawler explain in comments [not answers] here that fused words like "gonna", "hafta", "wanna" are the standard among native speakers when speaking, and that only in the most stilted and unnatural cirumstances are the full "going to", "have to", "want to" actually enunciated.
Unfortunately, I cannot find that comment now nor relevant posts either here on EL&U or our sister site Linguistics.se, so I can't confirm the scope of that assertion. It might only be certain fused forms or in certain situations. If anyone has any pointers, leave a comment, and I'll incorporate the information.
³ Anecdotally, I personally find myself writing wanna, gonna, etc in places I wouldn't have considered in years past. Things like text messages or IMs to close friends or family. And bear in mind that I'm one of those people who always properly capitalizes and punctuates text messages, and outright refuses to use modern innovations like u (you) or ur (your/you're).
The word gonna is the informal version. It's basically slang.
I would never write it in a paper, letter, email etc, but I probably use it a lot in friendly, casual speech.
informal: Going to.