Plagarisim?

What is plagiarism? The definition is to write someone else's words. Don't we do that everyday? In one way or another aren't we using someone else's words? While we word something to suit us isn't that still using their words? Everyday when we say good morning or hello aren't we in all reality plagiarising the person that originally used that phrase? I know I am asking questions that really have no answers yet, I feel better now that I have.
The past two weeks have made me think a lot about the weirdest things and this is one of them. I guess I am trying to figure out that if I was to die tomorrow what would my obituary say and what would they say in the eulogy. These are questions that I have no answer to, and yet in a way I really wish I could find the answers. Death is not scary to me I do know it is inevitable and a part of everyday life. How ironic is that? I know that I would and will miss many but will they feel the same? That I will never know.