expression, ichidan verb
give a reason; attach a reason
Used when someone provides or invents a reason for something, often with a nuance of justification or excuse.
遅刻の理由をつけるのに苦労した。
I struggled to come up with a reason for being late.
彼はいつも何か理由をつけて誘いを断
He always finds some reason to turn down invitations.