prefatory
adjective formal uk/ˈpref.ə.tər.i/ us/ˈpref.ə.tɔːr.i/
序言（性）的;作为开端的
coming at the beginning of a piece of writing or a speech
After a few prefatory comments/remarks, she began her speech. 几句开场白后，她开始了演讲。
Synonym: introductory (BEGINNING)