You want to know what good is and you think you'll find out by following a link on the web? Get real, we can't even tell you what is good, let alone what good is. Except that it's an adjective, or occasionally a noun, as illustrated here and in ancient Greek constructions like `the good,' except that they would do that with all kinds of nouns, so both pre- and post-Socratics could ask confused questions like ``what is the warm?'' [No, we don't have an entry for that. Write your own stupid web pages.]

Actually, Greek grammarians considered adjectives and nouns as the same part-of-speech, just as we consider demonstrative pronouns and possesive personal pronouns both to be pronouns, even though they play very different rôles in the language and cannot be interchanged.

Anyway, the important point is that it's not [good isn't] an adverb. So ``I speak English good'' is always false. (``I speak English well'' and ``I speak good English'' are probably also false, but only contingently.)

I apologize to sensitive readers for having used British punctuation convention for the second question mark. Please forgive me, you sanctimonious anal retentives. For another instance of the use of an adjective as a noun, see na czczo.