Revenge, avenge, and vengeance are all pretty close in meaning and spelling (there’s also scavenge, but that one’s just a coincidence; it has nothing to do with the others). All are related to
Okay. Interesting to me.
See, vindicare, meaning to avenge or punish, is also the root word for vindicate. Today vindicate means to justify or clear an accusation but back then, it was another synonym for revenge and avenge. Through the first decade of it life, vindicate meant that too, but in the sixteen thirties it took on the modern definition.
You can look further back in vindicare’s history by looking at vindication, the noun form, and its classical Latin equivalent vindicationem (yep, it also meant vengeance). It’s thought to come from vim dicare (to show authority), where vim is from vis—force—and dicere means “to say”. Dicere has mutated into words in several languages—in Spanish, dicer means “to speak” (wow, I actually remember something from the four years of Spanish I took in school) and here in English, we have the word diction. Dicere can also be traced to the Proto-Indo-European deik, which means “to point out” and is also a very distant relative of digit.
The final thing we have to look at is the prefixes that make avenge and revenge. Don’t worry. This won’t take long. The a- comes from ad-, which means toward or to(to get vengeance) and the re- is just used as an intensifier. The only real difference between these words is when they’re used. “To revenge” isn’t generally accepted in writing, probably because we have avenge to fill the gap. Revenge is, however, interchangeable with vengeance.
“French as a Mother-Tongue in Medieval England,” 2001, by Jacquie Heys.