一张的英语是 "one piece"。这个词来源于日语，在日语中 "一" 是 "ichi"，"张" 是 "wan"。结合起来就是 "一wan"，通过音译就变成了 "wan piece"，最后变成了 "one piece"。

例句：

I bought one piece of bread at the bakery. 我在面包店买了一张面包。
Can I have one piece of cake, please? 请问我能吃一张蛋糕吗？
One piece of evidence suggests that the suspect was at the scene of the crime. 有一条证据表明嫌疑人当时在犯罪现场。