The triangular theory of love

"The triangular theory of love is a theory of love developed by psychologist Robert Sternberg. In the context of interpersonal relationships, "the three components of love, according to the triangular theory, are an intimacy component, a passion component, and a decision/commitment component."
Intimacy – Which encompasses feelings of attachment, closeness, connectedness, and bondedness.
Passion – Which encompasses drives connected to both limerence and sexual attraction.
Commitment – Which encompasses, in the short term, the decision to remain with another, and in the long term, plans made with that other.

"The amount of love one experiences depends on the absolute strength of these three components, and the type of love one experiences depends on their strengths relative to each other." Different stages and types of love can be explained as different combinations of these three elements; for example, the relative emphasis of each component changes over time as an adult romantic relationship develops. A relationship based on a single element is less likely to survive than one based on two or three elements."
See more @ Wikipedia

More Info...

1. Triangular theory of love
2. The three components of love
3. The Triangular Theory of Love @ Science Based Life
4. 3 must have components for true love