Simple Definition:

A preposition is a word that shows the relationship between a noun or pronoun and another word in a sentence. It is used to indicate position, direction, time, manner, or purpose. [Noun: a person, place, thing, or idea] [Pronoun: a word used instead of a noun]

Examples:

• The cat is sitting on the mat. [On: showing position]
• She walked to the park. [To: showing direction]
• They will meet at 8 o’clock. [At: showing time]
• He played the piano with great skill. [With: showing manner]
• She went there for a job interview. [For: showing purpose]

Very Simple Definition:

A preposition is a word that shows the position, direction, time, or how something happens. It tells us where or when something is happening.

Examples:

• The cat is sitting on the mat.
• She walked to the park.
• They will meet at 8 o’clock.
• He played against his friend.
• She went to the shop before it closed.