What part of speech is -ical?

"-ical" is not a part of speech on its own. It's a suffix, meaning it's added to the end of a word to change its meaning or part of speech.

For example:

* Music (noun) + -ical = Musical (adjective)

* Log (noun) + -ical = Logical (adjective)

So, "-ical" itself doesn't have a specific part of speech. It's used to create words that are usually adjectives.