A collection of essays or papers on a particular subject by a number of contributors
a conference [n SYMPOSIUMS or SYMPOSIA]
a conference for the purpose of discussion [n SYMPOSIUMS]
A conference or meeting to discuss a particular subject
a convivial party as after a banquet in ancient Greece with music and conversation.
A drinking party or convivial discussion, esp. as held in ancient Greece after a banquet (and notable as the title of a work by Plato)
Symposium can refer either to a formal meeting at which experts discuss a particular topic, or to a collection of articles on a particular subject. Symposium has two plural forms: symposia and symposiums.