What part of speech is the word is?

The word "is" is a verb. Specifically, it's a linking verb, which connects a subject to a predicate.

Here's why:

* It expresses a state of being: "The sky is blue" ("is" shows the state of the sky)

* It links the subject to a noun or adjective: "She is a doctor" ("is" links "she" to the noun "doctor")

Let me know if you have any other words you'd like to identify!