N-COUNT
支柱;中堅
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...
魚和米是該國的主要食品。
This principle of collective bargaining has been a mainstay in labor relations in this country.
這一集體談判原則已經成為該國勞動關系的重要基礎。