即，也就是　that is or that is to say

　namely　用于对刚提及的事物给予更多的信息或说明。

　Only one boy was absent, namely Harry.　只有一个孩子缺席，就是哈利。
He could not do anything more than what he promised —namely, to look after Charlotte's estate.他只能做到自己答应的事，那就是照看夏洛蒂的产业。

［同义词］ that is, that is to say
［词源］古英语namly（就是这样的称呼）