substance  
noun uk/ˈsʌb.stəns/ us/ˈsʌb.stəns/
  (MATERIAL)        
 B2 [ C or U ]物质;材料 
material with particular physical characteristics
  an organic/chemical substance 有机/化学物质 
 What sort of substance could withstand those temperatures? 哪种物质能够承受那样的温度? 
 illegal substanceformal 毒品
an illegal drug
 - More examples
 - a natural substance
 - This substance is so radioactive that it glows in the dark.
 - This substance stretches to any shape you want.
 - Rubber is a flexible substance.
 - Two days after he'd been exposed to the substance, a painful rash erupted on his neck.
 
  (IMPORTANCE)         
C2 [ U ](某人)所说(或所写)的最重要的部分,要点 
the most important part of what someone has said or written
  Later that year, the substance of their secret conversation appeared in a newspaper article. 那年稍后,他们这次秘密谈话的要点出现在报纸上的一篇文章中。 
  [ U ]重要性;要旨;实质;根据 
importance, seriousness, or relationship to real facts
  There is no substance in/to the allegation. 这项指控毫无根据。 
 This new information gives substance to the stories we have heard. 这条新信息为我们听到的情况提供了根据。