No, “all” is not a preposition. It can function as a determiner, pronoun, adverb, or noun, depending on its usage in a sentence.
Uses of “All”:
- As a Determiner (Modifies a noun to indicate completeness or totality)
- All customers must follow the restaurant’s policies.
- She finished all her tasks before closing time.
- As a Pronoun (Refers to an entire group or amount)
- All is ready for the grand opening.
- He gave his best effort, but all was in vain.
- As an Adverb (Modifies adjectives or verbs, meaning “completely” or “entirely”)
- She was all alone in the kitchen.
- The menu was all new for the season.
- As a Noun (Refers to everything or everyone collectively)
- She lost all in the business.
- He gave his all during the restaurant’s busiest season.
Why “All” Is Not a Preposition
- Prepositions (e.g., in, on, under, about) show relationships between words in a sentence.
- “All” does not show a relationship between a noun/pronoun and another part of the sentence; instead, it functions as a determiner, pronoun, adverb, or noun.
Thus, “all” is not a preposition.