The word "forum" as used in English and many other modern languages obviously comes from Latin. It means a place where people gather to discuss, like an online forum or a scientific conference, but not a place of commerce. The Latin forum means a marketplace or an outside or public area. Is forum the best match for the English "forum" (with more or less equivalent reincarnations in other languages), or is there a better choice?
Caesar and Cicero refer to collŏquĭum in association with convenio vb and convenium noun.
a talking together, conversation, conference, discourse. (W Smith 1895)
collŏquĭum quum conveniunt in unum locum loquendi causa Varr L.L. 6,7,66.
and from Caesar B. G. 1
eo ad colloquium venerunt
in colloquium venire.
Is that too formal?
English in this context has a number of words that might originally have suggested something rather different. We speak of the Republican Party Convention, the Trades Union Congress, the Synod of the Church of England, the Welsh National Assembly, the Council for the Preservation of Rural England and so on. It wouldn't be stretching it too far to say that these are all forums of one kind or another.
Going into Latin, however, the most frequent word for a forum in the sense apparently needed here is conventus, basically meaning an 'assembly', a 'conjunction', a 'coming together', in almost any sense, and it's probably the most suitable word for 'forum' as the word is nowadays used. It appears far more often in word-searches than conventio, being much favoured (if that's the right word) by both Caesar and (especially) Cicero. A word like conventio, congressio or colloquium is tempting because of similarity in current English, but each seems to have had a restricted use, whereas conventus can be applied to any kind of gathering, including that of people for discussion and other kinds of interaction.