"Love is real, real is love,
Love is feeling, feeling love,
Love is wanting to be loved.
Love is touch, touch is love,
Love is reaching, reaching love,
Love is asking to be loved.
Love is you,
You and me,
Love is knowing,
We can be.
Love is free, free is love,
Love is living, living love,
Love is needing to be loved."--"Love" by John Lennon
I think love is much more then just a word or the instinct to mate. If all it is, is the need to reproduce then how do you explain gay animals? Love is an emotion felt by all creatures and although it can tie into having children that is not, to me, what it is at its core. I believe all beings can feel the emotion of love, of attachment to another being.
I think it is hard to pin an exact definition on love because it's one of the most complex emotions. But I think the best way to put it is the lyrics I posted above.