Simple Definition:

Prepositions are words that show the relationship between a noun [a word that represents a person, place, thing, or idea] or pronoun [a word that replaces a noun, such as “it” or “they”] and another word in a sentence. They often indicate location, direction, time, or manner.

Examples:

• She sat on the chair. (Shows the location of where she sat)
• The book is under the table. (Shows the location of where the book is)

Very Simple Definition:

Prepositions are small words that tell us where something is or when something happened.

Examples:

• The cat is on the bed. (Tells us where the cat is)
• We will have lunch after school. (Tells us when we will have lunch)