"Mine"

When I call you mine, it's not that I consider you mine in any sense of the word.  It's not that I think you'll ever be mine, either. Not like any person could really be owned by another, anyway.
What I mean to say is that you are my love. My light, my hope, my deepest desire. The ocean I want to drown in, the air I wish to breathe, the mountain I dream to conquer.

And when I say I am yours, that is exactly what I mean, in every sense of the word.