speech

(こうえん) Any public speech or talk given to a general audience. Authors doing a reading, dudes addressing the Friars’ Club, the graduation speaker at your  college, are all doing 講演.
 
(こうぎ) A lecture to a private group, a lecture at college.
 
セミナー A seminar.
 
(えんぜつ) A speech, usually political.