Learn what prepositions are and how they show the relationship between nouns, pronouns, and other words in a sentence. Find out the common types of prepositions, rules for using them, and common mistakes to avoid. Prepositions are parts of speech that show relationships between words in a sentence . In “the book on the table,” the preposition on shows the relationship between the book and the table. Learn about preposition , their usage, and examples. Understand how they connect nouns, pronouns, and phrases in sentences effectively.