What part of speech is at all?

"At all" is a phrase, not a single part of speech. It acts as an adverbial phrase, modifying verbs, adjectives, and adverbs to emphasize the extent or degree of something.

Here's how it works:

* "At" is a preposition.

* "All" is a pronoun or determiner, depending on the context.

Together, they form a phrase that intensifies the meaning of the word it modifies.

Examples:

* "Do you understand at all?" (modifies the verb "understand")

* "She wasn't at all interested." (modifies the adjective "interested")

* "He didn't move at all." (modifies the adverb "move")