What part of speech is the word work in sentence Susan arrives at early each morning?

The word "work" is not present in the sentence "Susan arrives at early each morning."

It appears you might be asking about the word "early" instead. In this sentence, "early" acts as an adverb.

Here's why:

* Adverbs modify verbs, adjectives, or other adverbs. They answer questions like "how," "when," "where," or "to what extent."

* In this sentence, "early" modifies the verb "arrives" by telling us when Susan arrives.