what are prepositions?

English as a Second Language English Vocabulary, Grammar and Idioms
1

Please explain more clearly “what are prepositions”.

Thank you.

Ruth

2

.
[i]A prepositions is a member of a closed set of items that

  • occur before a complement composed of a noun phrase, noun, pronoun, or clause that functions as a noun phrase, and
  • form a single structure with the complement to express its grammatical and semantic relation to another unit within a clause.[/i]
    .
3

thank you.

Ruth