that is to say

that is to say也就是说

【例句】

◆ Two weeks from today，that is to say the 1st of May, is my birthday．从今天起再过两周，也就是五月一日，是我的生日。 

◆ He's been ill—that is to say, he can't come to work today．他病了，也就是说，他今天不能来上班了。