Define love (what is love?)

As there are different kinds of love (romantic and friendship for example), I would say that generally it is the state in which one initially feels a closeness to someone/thing possibly out of novelty, later replacing those feelings with an obligation toward the same someone/thing.That's not to say that the obligation is not heartfelt, but more of a sense of duty and respect. I think this defines my idea of erotic and brotherly love.