We all agree that humans know what love is. We all agree that in some way, humans are capable of loving some things/people, and not loving other things/people. Such a definitive difference leads to other emotions, including rebellion, anger, hatred, repulsiveness, or on the other side of things, attraction, camaraderie, team spirit and unity.
As a Christian, I would take 1 Cor 13:4-8 as THE definition of love, which I am sure no one will deny to be true love, ideally:
Love is patient and kind; love does not envy or boast; it is not arrogant or rude. It does not insist on its own way; it is not irritable or resentful; it does not rejoice at wrongdoing, but rejoices with the truth. Love bears all things, believes all things, hopes all things, endures all things. Love never ends. As for prophecies, they will pass away; as for tongues, they will cease; as for knowledge, it will pass away. (1 Cor 13:4-8 (ESV))
Ideally, all of us should follow what is laid down here when loving, but of course this is an ideal situation. Less than ideally, most humans are not capable of doing this. As with many relationships, love is unable to bear and endure all things.
Why am I talking about all this? A recent spate of events has triggered this one particular thought: is the capacity for a human to love like a water tank? Is love a filling up process? My theory is this: when you love someone, you are filling their tank. When people love you, they are filling your tank.
How much love/care/concern can one person give to another, without returns, before that one person runs dry and can no longer love? How much can you pour out yourself, before you run dry? This is, of course, an extreme case. Very rarely do you love someone without them showing no love to you at all.