by Dhammanando »
In other words: (1) not-X, (2) free-from-X / without-X, (3) opposite-of-X, and (4) of unpredictable meaning that needs to be contextually determined..
1. Negative: channa, covered; acchanna, not covered.
2. Privative: agha, fault; anagha, free of faults.
3. Invertive: aggava, superior, anaggava, inferior.
4. Idiomatic: manussa, human; amanussa, "non-human", but not any kind of non-human; the word is limited to petas, yakkhas, pisācas and suchlike, and so is often translated as "spirit".
Now to come to my point, even if there was no commentary telling us that the a- in abyāpāda and avihiṃsā is an invertive a-, and that abyāpāda therefore means mettā and avihiṃsā means karuṇā, a competent translator would still need to at least reckon with this possibility. The fact that the a- prefix can be used in an invertive sense is indisputable.