No one says instant anymore. It’s always instantaneous. The former and the latter are nearly the same thing except the latter has more syllables. More is always better, right?
It’s just like irregardless and misunderestimated. You may think the extra syllables make you sound smarter, but I ain’t kidding, they aren’t real words and they make you sound foolish.
And yes, ain’t is proper English. It’s a contraction of ‘am not’. For some reason, English speakers dropped that contraction but kept all the other ones. English is weird that way.
For the record, instant can be a noun or an adjective where instantaneous is only an adjective. Instantaneous has a much narrower meaning, basically it’s a much shorter instant. Nearly every time people say instantaneous they should have said instant. The reverse is not true.
While we are on the subject, what’s with this obsession of using “I” as an object? (See what I did there?)
For some reason, saying “you and me” has been universally replaced by “you and I”. For example:
I thought she was going to give the book to you and I.
Wrong, wrong, wrong. “I” is always a subject, the doer of the action, remember? You use “me” when “I” becomes an object, the receiver of the action. For example:
You and I thought she was going to give the book to you and me.
Remember the old grade school test: does “I” or “me” work on its own? For example:
I thought she was going to give the book to me.
Me thought she was going to give the book to I.
At least we still have instant coffee. Or maybe not.