判断・推量N2
〜ことだから
knowing... / given that it's...
Structure
N + のことだから
Explanation
Expresses that because it is a certain (well-known) person or thing, one can infer the outcome. Follows noun + の, referring to someone or something known to both speaker and listener. The main clause often uses きっと…だろう or に違いない.
Examples
彼のことだから、きっと時間通りに来るだろう。
Knowing him, he'll surely arrive on time.
真面目な彼女のことだから、約束は忘れないに違いない。
Knowing how reliable she is, she's sure to remember the promise.
Note
The subject must be known to both speaker and listener; the main clause is usually a prediction about the future, not a past fact.