“Prepositions are words that connect a Noun or a Pronoun, or another Noun to indicate position or relation in time and space”.
“Prepositions is a word which is placed before a Noun or a Pronoun to show the relation in which the person, thing or action denote by the Noun or the Pronoun stands for something else”.
“A Preposition is a word used to show the relation of a Noun or a Pronoun to some other words in a sentence”.
Forms of Prepositions

Simple Prepositions

            At, by, with, on, to, for, of, off, from, though, up, till, over, under, after, etc.

Double Prepositions

            Into, onto, from among, from under, over, against, from within etc.

Compound Prepositions

            Compounds of Prepositions plus verb or adjective.
            Its examples are ‘Across’ (=on + cross); beneath (= by + neath);
            Beyond (= by + younder) etc.

Participle Prepositions

Present or past Participles used as prepositions as pending, concerning, considering, regarding, not withstanding, during, saving etc.

Phrase Prepositions

Those Prepositions which are made when two or more words are thrown together ending with a simple prepositions.