Is "onto" a word?
If it is, why not "upto", downto", "nearto", "backto", "outof", etcetera?
How do you feel about such constructions as: "in back of" (instead of "behind"), "off of" (instead of simply "off"), "outside of" (instead of the seemingly perfectly-adequate "outside"), and other modern usages?
>>Is "onto" a word?<<
Yes! You'll get onto it.
I would say "onto" is a more emphatic form of "on" in most cases, and slightly more literary. Thus, as I see it, both of the following forms are possible:
"You shouldn't take more responsibility on your shoulders."
"You should not take more responsibility onto your shoulders."
However, there may be cases where it seems more suitable to use "onto" than "on" in the specific (not figurative) sense of "on the top of" or "to the surface of". Thus:
"She tossed the book onto the table" seems to me to be more emphatic than "She tossed the book on the table". It somehow has more force.
Also, I feel it is better to use "onto" than "on" in the following sentence: "She was lying on her stomach on the beach, but rolled onto her back and sat up when she saw him coming in the distance."
By the way, there are other such "combined" prepositions, the most frequent being "upon" and "into". "Upon" is similar to "onto" in being a rather emphatic form, but of course it refers to a resting position rather than movement. Thus, the first sentence above could be re-worded as "You carry too much responsibility upon your shoulders".
It seems to me that "onto" and "into" came into being to express movement which ends on top of or within an object. It was not necessary to create prepositions like "downto", "upto", etc. since these prepositions involve such idea with verbs of movement anyway. See: "We ran up the hill laughing" or "The car raced down the street, then stopped".
Onto is indeed a word. Just like into. Why some words end up getting compounded into one and others don't isn't necessarily clear, nor does it always follow a set of rules. They just are.
"In back of" is a more dialectical way of saying behind, but it's logical and descriptive, and while I don't use it myself, it certainly doesn't bother me. "Off of" and "outside of" are extremely common and are not considered slang or colloquial, so what's the big deal?
The first and last time I ever heard "in back of" was on "Leave it to Beaver" ... or was that "Lost in Space"? ... one or the other. Yes, "onto" is a word but, no, it is not simply more formal than "on" rather it has a different meaning.
"onto" rhymes with "pronto" for me, and "outside of" and "off of" are also risibly ignorant. I notice that those who think they are acceptable gave no opinion on "downto" etc.
Wonder if they think that "maybe" should be used in the way often seen now: "They maybe wrong".