It can't be reduced to a definition. particularly when we have one word for so many different forms of love. The Greeks have eight different words and that's barely sufficient. Early this year in response to a prompt to define love, I wrote 11 minutes of poetry (with some prose mixed in). https://medium.com/write-under-the-moon/what-is-love-553648694528

That being said, here's something I wrote 11 years ago:

"The Beatles just covered the power of love for me. Now I can just paint me. I am a romantic. I believe in the existence of idealized love. I want it. I will find it. I want to grow old with my best friend, I want to walk down the streets of forever arm in arm. I want to sit on a park bench reading a book, her head in my lap reading her book as I stroke her hair. More important than sharing our highpoints, I want to share the mundane, and each other’s pain. That to me is true unconditional love. ...

Those who say this doesn’t exist say so because they don’t have it.

I want the intimacy — the connection. 'The purpose of a relationship is not to have another who might complete you; but to have another with whom you might share your completeness.' (From Conversations with God — Book 1). And sharing is primarily how I view sex. As Viktor Frankl writes, in addition to our primal need for sex, 'sex is a mode of expression of love…love is not understood as a mere side-effect of sex; rather, sex is a way of expressing the experience of that ultimate togetherness which is called love.'"