Definition of good:

part of speech: interjection

A word expressing approbation or admiration.

part of speech: noun

The contrary of evil; virtue; righteousness; benefit; advantage.

part of speech: adjective

The opposite of bad; pious; sound; undamaged; proper or fit; considerable; having sufficient; pleasant to the taste; unblemished; kind; favourable; clever; real- as, he is in good earnest; in the sense of wishing well- as, good- day, and good- bye.

part of speech: adverb

Well, as in the phrase as good.