responsible (形容詞/adjective)
責任がある
He is a responsible person.
irresponsible (形容詞/adjective)
無責任
She is a very irresponsible student.
---------------------
Basic Idioms:
---------------------
to be responsible for st: 《be ～》～に対して責任がある、~担当です, ~のせいです。
Examples:
You are responsible for doing your own homework.
I am responsible for this class.
Who's responsible for breaking this?
What are you responsible for at work?
I am responsible for ~.
--------------------------
Good set phrases:
-------------------
Please drink responsibly.

一切責任を負わない.
We assume no responsibility for ~.

安い建設資材のせいでビルが倒れた。
Cheap construction material was responsible for the building's collapse.
collapse= 倒壊

(交通事故の話)誰が悪かった？
Who was responsible?
Who fault was it?

responsibility=責任
Idiom: to take responsibility
Who will take responsibility for this accident?