I was taught that if there is only a single word after a preposition, it must be a Noun. For example,
Our blessings come from above.
If I was taught right, the word above after the preposition from is a NOUN.
However, I don't have any reference to the rule I mentioned above. And above is listed in the dictionaries as an ADVERB. So what am I missing here?
The word "above" can be used as a noun in a couple of limited, and one general way.
It can mean "heaven", "god" or metaphorically "the boss". This is what is meant in your quote. "Our blessings come from god/heaven"
The preposition "above" can also be used a noun elliptically, by removing the noun when the context makes the meaning clear.
Is the aeroplane above or below the clouds?
It is above.
Here the word "above" means "above the clouds", but the context makes it clear.
Dictionaries, especially learner's dictionaries, might not include all the rare senses and uses of a word. But remember that you can never say "above is a noun", only "above is being used as a noun in this sentence". Words only become parts of speech when they are used in a phrase or sentence.
Our blessings come from above.
Sorry, but you were taught nonsense!
Prepositions take a range of complements comparable to that of verbs: not just noun phrases, of course, but preposition phrases, adverb phrases and clauses (both finite and non-finite).
Trad grammar treats "above" as an adverb, but some modern grammars treat it as a preposition, in which case it's said to be 'stranded', i.e. not followed by the NP that is understood as its complement.
Whichever analysis is preferred, "above" is functioning as complement of "from".
