preliminary vs trial run

preliminary

noun
  • Any of a series of sports events that determine the finalists 

  • A preparation for a main matter; an introduction. 

  • A relatively minor contest that precedes a major one, especially in boxing 

adj
  • In preparation for the main matter; initial, introductory, preparatory. 

trial run

noun
  • An empirical test of the suitability or capability of a person or actor by letting him perform at least once. 

  • An empirical test of the suitability or effectiveness of a method or thing by running it at least once. 

How often have the words preliminary and trial run occurred in a corpus of books? (source: Google Ngram Viewer )