Is the word settled a common noun?

No, "settled" is not a common noun. It's a past participle of the verb "to settle," and it can function as an adjective, verb, or part of a verb phrase.

Here are some examples:

* Adjective: "The settled dust created a thick layer on the furniture."

* Verb: "The birds settled on the branches of the tree."

* Part of a verb phrase: "The argument was finally settled."

Common nouns are words that refer to general things, like "dog," "chair," or "city." "Settled" doesn't fit that definition because it describes a state or action rather than a concrete object.