He has done it by exploring, by experimenting, by developing his own model of the grammar of language, by trying it out and seeing whether it works, by gradually changing it and refining it until it does work.
出自-2010年6月聽力原文
英語六級真題
The major components of our energy systems, such as fuel production, refining, electrical generation and distribution, are costly installation that have lengthy life spans.
2015年12月六級真題（第一套）閱讀 Section B
柯林斯高階英漢雙解學習詞典釋義
VERB
提煉;精煉
When a substance is refined, it is made pure by having all other substances removed from it.