abstract noun       
noun [ C ] uk/ˌæb.strækt ˈnaʊn/ us/ˌæb.strækt ˈnaʊn/
 抽象名词
a noun that refers to a thing that does not exist as a material object
  "Happiness", "honesty", and "liberty" are abstract nouns. “幸福”、“诚实”和“自由”都是抽象名词。 
 Compare: concrete noun