ABSTRACT
Lectures have a long history, probably originating about the time humans developed speech. We define lectures as scheduled, didactic presentations to a group by one or a few speakers who plan their remarks in advance of the presentation. We distinguish lectures from theatrical productions that follow a script and from impromptu comments or tutorials. In preparing their presentations, lecturers typically have some idea about their audience. They may or may not have a set time limit, but most lectures are under two hours in duration.
