What's the most important thing in a relationship?

I think all the 4 are important, but first and fore most if you love a person then you should trust. So trust and love apart from the other two

these are inter related concepts. Of you love, you will trust and communicate and have understanding.

Trus is most necessary, however. Love is a natural feeling and this may not always be strong enough. But when you are in a relation, this creates mutual obligations that need mutual trust. Witout trus, there will be no understanding and communication meaningless.

A relationship is like a company; It requires multiple things in order to survive, or it will collapse. No one thing is more important than another. Although the biggest ones would probably be (in my opinion) (true) love, and trust.

Love.

Without this everything else is trivial.

I think all these four ingredients are necessary in a good and everlasting relationship and in the absence of one ingredient all the other ingredients doesn't hold that much significance....In a close and important relationship all the four ingredients should remain there and the lesser these ingredients are the lesser is the the value of the relationship...

Trust is the main thing in the relationship...

Trust is the most important thing in a relationship.

To give birth to a great relationship two persons should have matching mindset. If your thinking matches, automatically everything starts falling in place.