I know both of their meanings however I have heard both.
My sentence is…
…we are fastly becoming the areas elite…
is that correct?
Or is it more common to say vastly?
Good search found more “vastly becoming”
thanks
Fast is a word that doesn’t take “-ly” as an adverb, so it would be “fast becoming,” if you’re talking about becoming [something] in a rapid manner.
“Becoming” can also mean “giving an attractive appearance,” so the “vastly becoming” hits probably refer to something that is vastly (i.e., extremely) attractive – e.g., That bonnet is vastly becoming to you, my dear.
Google Fight!
fast becoming = 749,000 hits (the grammatically correct phrase)
**fastly becoming ** = 3,560 hits (the grammatically incorrect phrase used .07% of the time. In the first 50 hits, only one cite misused this to mean ‘very pleasing’; all the other uses meant ‘quickly happening’).
vast becoming = 182 hits (obviously typos and poor spelling)
**
vastly becoming** = 947 hits (only four hits in the first hundred used this to mean ‘very pleasing’; the rest meant ‘quickly happening’ or even ‘happening on a vast scale’)
Conclusions from web usage:
If something is ‘becoming’ used as an adjective, that is, ‘pleasing’ or ‘pretty’ and it is pleasing in a grand way, then it is 'vastly becoming.’
If you mean something is happening quickly (especially transforming from one quality or quantity to another), then you use 'fast becoming.’
If something is happening (esp. transformatively) at a large or even all encompassing (i.e., vast) scale, then 'vastly becoming’ may be correct. However, to use this simply to mean quickly is wrong.
‘Fastly becoming’ and ‘vast becoming’ are just wrong.
What’s the whole sentence you’re trying to sculpt?
“Fast becoming” just sounds a little trite to me and I wonder if there’s a better way to word it.
Of course, too many cooks spoil the chicken. 
If you’re descriptionist to the extent that you believe grammar as used on the Internet is a valid way of determining correct usage, is the correct spelling of Pfizer’s virility-promoting drug ‘V|@gra’, ‘V|@gr@’, ‘V|agra’, or ‘/|@gra’? =)
Such as, oooh…“quickly becoming”. Problem solved.
“Vastly becoming” doesn’t make sense. “Vast” refers to great sizes or amounts.
Vastly: Very great in degree or intensity
Right. While something can become great in degree or intensity, I don’t think it can ‘become in a way that is great in degree or intensity,’ which is what “vastly become” should mean.
‘Becoming’ is a verb - so ‘vastly’ is the adverb. It describes the rate at which the becoming is taking place. Nothing wrong with that.
Exactly. At best it’s awkward and is not how you’d normally use the word ‘vast’ or ‘vastly.’ It says that the becoming is happening in a way that is great in degree or intensity. ‘Become’ in this sense is usually modified in terms of rate, not degree. In any case I don’t think that fits the OP’s sentence. The nation is changing fast, not vastly.
I don’t follow. Can you give an example?
It’s possible for a fast change to be minor, or a slow change to be vast, or a vastly-changing environment to involved gradual change over a long period, or…or…etc.
(I long ago made a post that pointed out there’s plenty other options that just don’t sound as silly as anything involving ‘vastly’, such as ‘quickly’, ‘suddenly’, ‘impetuously’, ‘irresponsibly’, take your pick…
“The nation is quickly becoming polarized.”
“The planet is slowly becoming a wasteland.”
“The calf is gradually becoiming a bull.”
vs.
“The Sun is intensely becoming a fireball.”
“The pants are greatly unravelling.”
“The concrete is immensely solidifying.”
Sorry, I went adrift on the last two. They should have read:
“The pants are greatly becoming unraveled.”
and
“The conrete is immensely becoming solid.”
And I shouldn’t have spelled ‘becoming’ wrong either. :smack:
Hey, don’t start introducing extraneous strawman verbs into this - we’re talking about “to become” only 
…
So if the adverb can’t describe the rate of change, what about:
“The situation is gradually becoming dangerous”
or
“We are increasingly becoming worried about…”?
No, wait, that’s the wrong set of comments:
Try…
“The situation is defintely becoming worrying”
“I can see this argument potentially becoming a non-sequitur”
I’m not sure what word I’m looking for, but those don’t describe a degree of change the same way that ‘intensely’ or ‘greatly’ do. Those two words describe the certainty of something happening, not how intensely it’s happening.
Descriptionists know the difference between usage and abusage. 