"Disgraceful" and "ungraceful" are both derived from negations of "graceful". Wiktionary describes disgraceful as bringing or warranting disgrace; shameful. giving offense to moral sensibilities ...
Possible Duplicate: Why “unequal” but “inequality”? Origins of negative prefixes like in-, un-, il-, ir-, dis-, a- There are a lot of prefixes for meaning ...
I've read here about origins of in- and un- negative prefixes. Are there any known origins of other negative prefixes such as il-, ir-, dis-, a-?
Are there any patterns to observe in choosing the correct prefix to use? There are other prefixes as well, but these are usually the ones I mix up. As in unbelievable, disproportionate, asymmetric, ...