The farm buildings form three sides of a square.

这几栋农舍构成一个正方形的三个边。

《牛津词典》

For instance, subjects are given three words such as "age", "mile" and "sand"—and asked to come up with a single word that can precede or follow each of them to form a compound word.

例如，给受试者三个单词，如“年龄”、“英里”和“沙子”，并要求他们想出一个单词，这个单词可以在这三个词之前或之后组成一个复合词。

youdao

After forty days without a fish, the boy's parents had told him that the old man was now salao, which is the worst form of unlucky, and the boy had gone with another boat which caught three good fish the first week.

四十天没钓到一条鱼，男孩的父母告诉他，老人现在是“撒劳”了，这是最倒霉的倒霉事。于是男孩和另一条船一起去了，这条船在第一个星期就钓到了三条好鱼。

youdao

If there were such a thing as a cubic acre, three of them would form a cube 300 feet on a side.

FORBES: Sorry Paul Krugman, But We Still Need Say's Law

This is a form of rotational symmetry, since the three votes form a rotating cycle.

ECONOMIST: The mathematics of voting

Membership has fallen from eight to six, three of whom are required to form a tribunal to hear any appeal.

BBC: Guernsey's property tax appeal panel needs more members