overture
/ˈəʊvəˌtjʊə(r)/noun
1- an orchestral piece at the beginning of an opera, suite, play, oratorio, or other extended composition（歌剧、组曲、戏剧、清唱剧, 或其他长篇作品的）序曲。
1.1
- an independent orchestral composition in one movement（乐章内的）独立乐段。
1.2
- an introduction to something more substantial序曲, 序幕：
the talks were no more than an overture to a long debate.
谈判只不过是一场长时间辩论的序幕。
1.3
- （一般作overtures）an approach or proposal made to someone with the aim of opening negotiations or establishing a relationship（为开始谈判、建立关系而作出的）主动表态, 姿态; 建议：
Coleen listened to his overtures of love.
科丽恩听着他求爱的表白。
词源
late Middle English (in the sense aperture)： from Old French， from Latin apertura 'aperture'.