I’m going to be the contrary Brit - I prefer “fall” and wish we used it. (We don’t, so I use autumn - I’m not that contrary).
Reasons are - 1) it’s needlessly latinate - if our other seasons were Vern, Estus and Hiver that would be fine but they’re not so why borrow from Latin for this one? 2) It foregrounds the relationship between time of year and the natural environment. 3) Relatedly, it pairs nicely with spring, giving some symmetry. 4) Spring forward, autumn back is a terrible mnemonic.
In sum, “autumn” feels contrived and detached from reality, an imposition from the Latin-schooled elite while “fall” feels like the natural language of people talking about what they see around them.
I have the feeling that this is not completely correct and that autum is not derived directly from Latin, but that it is more akin to the French - Norman dichotomy shown in mutton/lamb, pork/pig, beef/cow, poultry/chicken and so on/etc. So the USA prefers fall? It figures.
It’s weird, I think ‘autumn’ sounds nicer, but I never actually use it and find it odd when people do. I guess instinctively I feel it’s more of a literary word than a spoken word.
Well, when it comes to modern English, a huge portion of our routine vocabulary is needlessly Latinate. Unless you’re an expert, you would probably have to do a modicum of research to expunge all the Latinate influences in this message and recast it with words of purely Germanic origin.
It’s context dependent. I can’t actually tell you what the necessary context for each is, but I know it when I see it. Basically, one or the other will seem more “correct” to me, depending on the scenario.