1、foot 表示“脚”时，其复数为 feet。如：

I wear shoes on my feet. 我脚上穿着鞋子。

He is on his feet for sixteen hours a day. 他每天站16个小时。

He suffers terribly with his feet. 他的脚痛得不得了。

I walked into a pool of water and got my feet wet. 我走近一个水坑，把脚弄湿了。

2、foot 表示“英尺”时，其复数是 feet 或 foot。如：

Jim is six foot [feet] tall. 吉姆6英尺高。

The snow is three foot [feet] deep. 雪有3英尺深。

The tree is six foot [feet] around. 这树周长6英尺。

The table is six foot [feet] long, or about two meters long. 桌子有6英尺(或2米)

3、但在复合形容词中通常用单数。如：

a six-foot-tall man 6英尺高的人