arc  
 noun [ C ] uk/ɑːk/ us/ɑːrk/
  (CURVE)      
  弧;弧状;弧线;弧形
the shape of part of a circle, or other curved line
  The ball rose in a high arc and fell behind the boundary line. 球在空中高高地划了一条弧线落在边线外。 
   (ELECTRICITY)     
  电弧,弧光
a powerful flow of electricity that goes across a space between two points
   (STORY)      
 (电影、书籍或电视剧的)故事情节,支线故事
a complete story or the story of one character, especially one that is part of a larger story in a film, book, or television series
  Even the minor characters in these films come with their own story arcs.  即使是这些电影中的小角色也有自己的故事情节。 
 Films about teachers working with troubled kids tend to follow a predictable arc involving conflict and resolution. 关于教师与问题儿童的电影往往遵循这种预料之中的故事情节——发生冲突和解决冲突。 
 arc  
verb uk/ɑːk/ us/ɑːrk/
  (CURVE)      
  [ I ]循弧线行进;做弧形运动 
to move in the shape of an arc
  The rocket arced gracefully into the sky. 火箭升空,在空中划出一条优美的弧线。 
   (ELECTRICITY)     
 [ I usually + adv/prep ]形成电弧 
to make an electric arc