DEAREST (adjective) definition and synonyms | Macmillan Dictionary.

What type of word is dearest?

adjective [ADJECTIVE noun] When you are writing to someone you are very fond of, you can use dearest at the beginning of the letter or email before the person's name.

Is it correct to say my dearest?

Dear is usually used to address people at the start of a letter or email (Dear Mr. Smith) or as a pretty formal way to regard someone in conversation, however, it's usually only used by the upper class and elderly. Dearest is used as a form of address too, but often goes with people you care deeply for.