What part of speech is used to?

"Used to" is a phrasal verb. It functions as a single unit with a specific meaning, which is different from the individual meanings of "used" and "to".

Here's why it's not just a preposition or an adjective:

* Preposition: Prepositions show the relationship between a noun or pronoun and another word in the sentence (e.g., "on the table," "in the house"). "Used to" doesn't express a spatial or temporal relationship like a preposition does.

* Adjective: Adjectives describe nouns or pronouns. "Used to" doesn't describe anything in the sentence.

"Used to" is a phrasal verb because it acts as a single verb:

* Indicating past habit: "I used to play basketball every day."

* Indicating a past state: "She used to be a teacher."

It's important to note that "used to" can also be part of a longer phrase, such as "get used to" or "be used to," which can also act as phrasal verbs.