在三楼英语怎么说

"在三楼"在英文中的常用表达是"on the third floor"。来源是因为楼层数通常会从一楼（ground floor）开始计算，因此第三层就叫做"third floor"。

例句：

"I live on the third floor of my apartment building."（我住在公寓楼的三楼。）
"The meeting room is on the third floor of the office building."（会议室在办公楼的三楼。）
"The elevator doesn't go to the third floor. You'll have to use the stairs."（电梯不能到三楼，你得用楼梯。）