For words like forum and datum, both are possible, but also there's a clearly more commonly used option that doesn't confuse everyone. In Dutch, fora is probably about equally common as forums; in English I'm not sure I've seen it ever used. It's like using datum to mean a single data point: "look at me being clever about word technicalities and making everyone do a double take to understand this sentence". At least, that's how I feel when seeing a native speaker use datum instead of data point in English, or in Dutch using data to mean multiple calendar dates (the common word being datums).
I don’t know when I internalized that “data” is plural and its singular is “datum”, but it wasn’t when I had a similar reaction to “fora”. The former is just how my brain handles the word’s count, and the latter is very much like your reaction.
Personally, I'd go for "forums." (I don't actually think I've ever actually heard "fora," so I'm skeptical that it's even used enough to qualify as a "valid" English word...)
Hah, I fought a battle for months at a Nordic automotive OEM, to try to stop them from overusing "fora", to no avail. They were so convinced that it was the proper word to use, they also used it in singularis, as in "We will bring that up in another fora", often then also referring to a single meeting to be held in the next day. This is only one tale out of many on how corrupted the corporate Scandinavian English can be, and sadly, since being essentially marinated in this parlance, I can probably only detect and reflect of a fraction of the linguistical felonies committed around me, and worse: by myself.
You are technically correct, the best kind of correct. But in reality correctness in language is dictated by usage. After all, their r hella many formerly “correct” parts of language no1 uses ne more or sth.
Otherwise we’d still be speaking proto-Indo European arguing about words that came from whatever language came before that.
