N-COUNT
支柱;中坚
If you describe something as the mainstay of a particular thing, you mean that it is the most basic part of it.
例句
Fish and rice were the mainstays of the country's diet...
鱼和米是该国的主要食品。
This principle of collective bargaining has been a mainstay in labor relations in this country.
这一集体谈判原则已经成为该国劳动关系的重要基础。