I teach science to high school students. The other day I was teaching respiration to a class and the topic was Aerobic and Anaerobic Respiration. And I said Aerobic respiration is the kind of respiration that takes place in presence of oxygen. Anaerobic respiration is the kind of respiration that takes place in absence of oxygen. Here 'an' is the prefix used to denote the opposite of Aerobic. So one of my students asked me what other opposite words can be made by prefixing 'An-'. I tried googling but didn't find any such pair of opposites.
Is this the only case where An prefix makes an opposite of a word or are there others. If you could list some pairs it would be helpful.