Defining love would be like defining an 'ocean'. Every time you take a plunge into the ocean you are bound to find something new and novel. This is because of the human psyche which is different for different individuals. What could be said to apply to one may fail in case of some other individual.

But there exist some common threads which bind people in love.

Some such tenets which help while defining love are:
is all about accepting

Accepting is an unconditional mutual agreement between the two individuals in a relationship. It could be said that acceptance is about labeling someone as "okay" and having no particular desire to change them.
means appreciating

Appreciation is the next step to acceptance. It is about coming to terms you're your relationship and your partner. True love is about coming to terms with the all the lacuna and accepting a person and relationship in its natural form.

A good relationship comes about when you come to terms with your likes about the other person in the relationship.
is wanting and making another person feel good

In the case of true love, both partners try and strive to make things happy for the other.
is about being unconditional in nature

Make love unconditional in nature and only then would it have the best of foundations to becoming a long and lasting relationship.
is about imparting a sense of security to your relationship

So, for a successful relationship, it is always better that you contribute the maximum and make your partner feel secure about the relationship.
is about ignoring the trifle little details

If you come across little things that irritate you about your partner, then the better thing to do would be to talk it over and find a solution rather than make a problem out if it! Also you could see the issues and still love your partner for he / she might be worth much more than a trifle little issue!
is about patience and trust as the foundation

A relationship is all about giving each other time and lending an assurance. Trust is another important element in a relationship as it acts as cement which holds it together during adverse times.
is about keeping envy out

In love, at times is better for the 'I' to take a back seat. It is about 'we' and not about 'I'. So for the longevity of your relationship, sink elements such as envy and individual haughtiness!
is about perseverance

In case of true love, mistakes do happen but learning from mistakes is more important. At times, you would need to persevere to make amend to ensure that your love survives the test of times.
is about hope and being true

is about being true to yourself and to your partner.
It is all about hope, hope that you would be there for your partner during the best and worst of times