Learn English – Word/phrase to mean something that just happens once


What is the word/phrase to mean something that just happens once? For example,

I have often been told/expected to do this and not to do that. I become aimless
and gradually lose the idea of who I am. I ask myself "What is the point?" If
life is just once thing, why can't I live my life in my own way,
the way I think is right and suitable to me? If I cannot, I would
rather live a shorter life.

Best Answer

In your example you could say, "if life is lived just once." Alternatively you could say "a one-time event."