Colloqui-

The plural of colloquium is colloquia. See -um in Latin.

Colloquium is a Latin word, meaning: a conference, seminar or a meeting for a discussion. (The original has co- for 'together' and loqu- for 'to speak'.) It is nearly always used in academic circles. As academics, particularly the older ones, are fond of the traditions of Latin, it is best to use the form of the plural that Latin would use.

You might also like to see Symposium.