If that's how we're defining digital textbooks, there's no hope of that becoming a mainstream product.
出自-2013年6月閱讀原文
英語六級真題
As Yale law professor Anne Alstott argues, justifying parental support depends on defining the family as a social good that, in some sense, society must pay for.
出自-2010年6月閱讀原文
Economic inequality is the "defining challenge of our time".
2015年12月六級真題（第三套）閱讀 Section C
柯林斯高階英漢雙解學習詞典釋義
VERB
闡明;規定;限定;使明確
If you define something, you show, describe, or state clearly what it is and what its limits are, or what it is like.