A plenary session (with a plenary speech or plenary talk) is derived from the Latin root plenarius meaning "full" or "absolute". It usually refers to a session in a conference which is open to all (or a large number) of attendant speakers, who may each contribute prepared or ad-hoc material. Plenary sessions are typically scheduled both near the start of a conference, and in the latter half, but not typically at the final hour, due to many attendees leaving before the last day. Various prominent speakers often give opening plenary speeches, at the start of a conference, or closing plenary speeches, in the final plenary session. During those sessions, typically all other activities are suspended, or exhibit halls closed, to allow everyone to attend the plenary talks or sessions.
These sessions may contain a broad range of content from keynote speeches to panel discussions and are not necessarily related to a specific style of delivery.