preamble
noun /ˈpriːæmbl/
  /ˈpriːæmbl/
 [countable, uncountable] (formal)- an introduction to a book or a written document; an introduction to something you say
序言;导言;前言;开场白 -  in a preamble The aims of the treaty are stated in its preamble.
条约的宗旨已在序言中说明。  -  preamble to something the Preamble to the US Constitution
美国宪法序言  -  without preamble She gave him the bad news without preamble.
她开门见山地把坏消息告诉了他。  
词源late Middle English: from Old French preambule, from medieval Latin praeambulum, from late Latin praeambulus ‘going before’. -  in a preamble The aims of the treaty are stated in its preamble.