mainstay

1. N-COUNT If you describe something as the mainstay of a particular thing, you mean that it is the most basic part of it. 最基本组成部分[usu 'the' N 'of' n]

Fish and rice were the mainstays of the country's diet. 鱼和米是这个国家的主要食物。

This principle of collective bargaining has been a mainstay in labour relations in this country. 这种集体谈判原则已成为该国劳动关系的一个重要基础。