In chemistry, a now antiquated naming system designated different oxidation states of metals using "-ous" for lower and "-ic" for higher. For example, ferrous (Fe2+) vs. ferric (Fe3+) and cuprous (Cu+) vs. cupric (Cu2+). The naming system is presumably French in origin because it uses Latin names for the elements and because "-ous" and "-ic" are typical French suffixes (suffices?).
A while ago I wondered whether such word pairs existed outside of chemistry and also whether they reflected degrees of whatever they were modifying. I put the question out there and got some feedback:
Sixty Grit said: harmonious vs. harmonic;
Pete tweeted: numerous and numeric;
Jason tweeted tonous and tonic;
Blake tweeted vampirous and vampiric.
"Tonous" and "vampiric" come up as questionable words. I added generous and generic, tyrannous and tyrannic, and barbarous and barbaric to the list.
Of these pairs, barbarous and barbaric come the closest to what I sought: barbaric sounds slightly more barbarous than barbarous does.
Can you add any word pairs? I will update this post with contributions.
Michael Haz adds sonorous and sonoric; calorous is failing my dictionary.
rhhardin adds autonomous and autonomic.
Brill adds coprophagous and coprophagic
Deborah adds amorphous and amorphic