Brian Thornton wants to know if I can explain the use or misuse of the adverb off: should we use it alone or with the preposition of. Should we say, “The cat jumped off the table” or “off of the table”?
Well, maybe I can at least define the problem. The adverb off is in the process of becoming a preposition. As an adverb, its object requires the preposition of: “The button flew off [of my shirt].” As this word becomes more and more a preposition itself, the additional preposition of becomes redundant: “The button flew [off my shirt]”. (I used square brackets here to set of the prepositional phrases.)
I am speaking only of the adverb off. Like many words in English, this word has several functions. It is also a prefix (an off-white dress), and adjective (the lights are off), and a verbal particle (Lenny took his hat off). It started out as an adverb, though it apparently was never happy in that function and hence is currently changing careers. While it is in the process of change, we should use whichever form those around us are using; both forms are correct.
This historical shift is not unusual. Out is another example of an adverb becoming a preposition. Out, too, is still used mostly with a preposition to mark its objects: “Melvin came out [of the house]”, “Lucinda Head is out [of her mind]”. It has picked up a new meaning, however, “out through”, and in that sense, of cannot be used: “The dog sniffed his food once and flew [out the door]”. Out is lagging materially behind off in its career shift but it seems to have begun the journey.
Many other adverbs are prepositions and conjunctions: after and before may be all three:
• I’ve never seen him before. (Adverb)
• I saw him before he grew the beard. (Conjunction)
• I knew her before the war. (Preposition)
I’m sure you can think of others. Nothing amiss here: multifunctional words that belong to several categories are commonplace in all languages.
Language is not stagnant. It is changing all the time. Language change is not simply the coming and going of words; that is the least interesting change in language. Words are shifting from one category to another, the categories themselves are changing, syntactic structure is changing, juggling words as it goes along. All this is taking place now right under our noses, where tongues and lips are constantly churning out grammar and vocabulary, producing nuances that eventually add up to new dialects and even languages.