I thought of this one when I was writing up my post on some time, sometime or sometimes. The word erstwhile popped into my head, and I thought that I’d better check if it officially meant something different from sometime.
Erstwhile means former as an adjective and formerly as an adverb: “Her erstwhile lover was now a senior politician”.
Sometime as an adjective means former; as an adverb it means at some unknown/unspecified time, with formerly marked as an archaic use in most dictionaries that I checked. In American English, it is also used for occasional.
I like erstwhile. It’s a nice, odd word that’s a bit hard to type. Let’s try to keep it going, even if it does essentially mean the same as sometime!