A plenary session or plenum is a session of a conference which all members of all parties are to attend. Such a session may include a broad range of content, from keynotes to panel discussions, and is not necessarily related to a specific style of presentation or deliberative process.
The term has been used in the teaching profession to describe when information is summarized. This often encourages class participation.
The Congress of Vienna is an example of a congress that did not meet in plenary sessions.
When a session is not fully attended, it must have a quorum—the minimum number of members required—to continue process.
Some organizations have standing committees that conduct the organization's business between congresses, conferences, or other meetings. Such committees may themselves have quorum requirements and plenary sessions.