该句属于英语“减法表达法”之一：

1. “减数 + fewer/less than + 被减数 + leaves/is + 余数”：

One fewer than five is four.

One less than five is four.

【翻译】5 - 1 = 4  （含义：比5少1是4）

跟下句有异曲同工：

2. “减数 + from + 被减数 + leaves/is + 余数”：

One from five leaves/is three.

【翻译】5 - 1 = 4  （含义：从5中去掉1 是4）