负一用英语说是 "negative one". 来源是数学领域，是数轴上小于零的一个数。
一些例句如下：
The temperature outside is negative one degree. (温度在外面是零下一度)
The result of dividing five by negative one is negative five. (除以负一的五的结果是负五)
Negative one represents the opposite direction on the number pne. (负一代表数轴上的相反方向)