婚姻是一个已存在数千年的习俗。

Marriage is an ___institution that has existed for thousands of years.

在许多文化中，婚姻这一习俗仍然受到高度重视。

In many cultures, the ___institution of marriage is still highly valued.

全民教育是现代社会的一项基本制度/习俗。

Universal education is a fundamental ___institution in modern society.