The Zen Buddhist literature does not specifically answer this question but rather looks at its attributes and attitudes, which constitute true or genuine love.
Here are the love attributes described by the Buddha himself during his 50 years verbal teaching 2500 years ago.
Therefore one can summarize the definition of genuine love in Zen Buddhism as follow:
Wanting others to be happy without expecting anything in return from them.
True love is altruistic and non-conditional. It is not a “given-take” feeling.
Is it our current understanding of the word “love”? “Are we misusing the meaning of the word”?
This love described above is truly unconditional and requires an enormous courage, generosity and tolerance (including self-acceptance). On the other side conditional love or self-centered love is giving something as long as something else is received in exchange. This “give and take” is more a “trade contract” than true love and will always create attachment since one becomes attached not only to the other person but also to what this person is providing.
When we become attached we cannot foresee ourselves becoming alone despite the fact that everything and everybody are transient. The fear is based not too much on what we are giving but on what we are getting back physically and emotionally. This maybe why death is perceived as a loss even if we do not own anything or anybody.
This distinction between unconditional and conditional love means that 'love' in Zen Buddhism and other religions refers to something quite different from the ordinary term of love that we are all using and misusing.
What is the difference between love and attachment?
The meaning of the word “love” that we are using all the time is usually about attachment such as living together, successful commune relationship including sex, money, family, friends, sharing the good and the bad, etc. This is always with some degree of self-interest.
Attachment and love are similar in that both of them draw us to the other person or object. But in fact, these two feelings or emotions are very, very different. When we’re attached we’re drawn to someone because he or she meets our needs and expectations. In addition, there are a lot of subconscious strings attached to our attached affection. We are aware that these strong subconscious strings are there. For example:
With attachment, we go up and down like a yo-yo, depending on how the other person treats us. We question:
This is not very peaceful, is it? We’re definitely stirred up.
There is nothing wrong to being attached to someone or something as long we realize that the “de-attachment” when occurring – and it will- can and will be very painful.
On the other hand, the Love from Zen teaching and from any other religions is more unconditional and spiritual.
We simply want other to have happiness and serenity without any strings attached, without any back expectations that is what people will do for us or how good they will make us feel. Instead, in Zen Buddhism and any other spiritual schools true love refers only to detachment and the unselfish interest in others' wellbeing, happiness and serenity regardless your own consequences. Very hard, if not impossible, to follow or to accept.
Thank you. Ven. Ji Gong Sunim Nov. 2015.