particle  
noun uk/ˈpɑː.tɪ.kəl/ us/ˈpɑːr.t̬ə.kəl/
  (GRAMMAR)      
  [ C ]小品词,语助词 
a word or a part of a word that has a grammatical purpose but often has little or no meaning
  In the sentence "I tidied up the room", the adverb "up" is a particle. 在句子 I tidied up the room 中,副词 up 是个小品词。 
 - More examples
 - A phrasal verb is a verb consisting of a verb plus a particle.
 - He often comes out with the wrong particle.
 
  (SMALL PIECE)         
C2 [ C ]微粒,粒子 
an extremely small piece of matter
  Dust particles must have got into the motor. 发动机里一定是进灰了。 
 Electrons are atomic particles. 电子是原子粒子。 
  [ S ]极小量 
a very small amount of something
  She wouldn't give me even the slightest particle of information about what she'd been doing. 对于她所做的事情,她一丁点消息都不会透露给我。