In couples therapy, one of the first things I do is to introduce a model of love and encourage partners to use this model to understand their own relationship. Developed by Yale psychologist Robert Sternberg, Ph.D., the Triangular Theory of Love characterizes love relationships as being constituted by different combinations of three elements: Intimacy, Passion and Commitment. Different types of love can be described by different combinations of these three elements. A relationship based on a single element is less likely to last than one based on two or more elements. The relative emphasis of each component changes over time as an adult romantic relationship develops.

• Liking includes only one of the love components: Intimacy without passion or commitment. In this case, “liking” is not used in a trivial sense. Intimate liking characterizes a developing friendship in which a person feels a bondedness, a warmth, and a closeness with another, but without intense passion or long-term commitment. When I worked for PepsiCo International, I had many occasions to sit next to get to know people on long international flights. Hours of conversation later, I would feel a sense of mutual visibility and liking with this person. I call this relationship the “would-be best friend.”
  

• Infatuation also includes only one component: Passion without liking or commitment. This is "love at first sight" or what is better captured by the phrase “lust at first sight.” But without the intimacy and the commitment components of love, infatuated love may disappear suddenly. We have all known people who can meet someone and have sex with them the same day. Do they get to know each other and feel intimacy? No. Is there any real commitment for the future? No. I call this type of relationship “The Fling.”
  

• Empty Love consists is the third form of love that only has one component: Commitment without intimacy or passion. A stronger love relationship can deteriorate into one in which the commitment remains, but the intimacy and passion have died. Also, relationships often begin as empty love in cultures in which arranged marriages are common. So what is the “glue” that keeps a couple together when there is no intimacy and passion? Religion, the children, illness, fear of being on one's own--these are some of the motivations I've seen for people in empty love relationships. This kind of relationship might be labelled “The Obligatory Marriage.”
  

• Romantic Love is a combination of intimacy and Passion. Romantic lovers are bonded emotionally (as in liking) and physically through passionate arousal. But the level of commitment is relatively lacking. I recall a woman who spent years in love with a married man. They shared deeply held values and beliefs and had many common interests. And they had hot sex. But he had children and would not abandon his commitment to his family. His relative lack of commitment to her was apparent when he was unable to be there for her during a serious illness. This type of relationship might be called the “The Affair.”
  

• Companionate Love consists of Intimacy and Commitment. This type of love is often found in marriages in which the passion has gone out of the relationship, but a deep affection and commitment remain. I call this type of relationship “The Best Friend.”
  

• Fatuous Love has the Passion and the Commitment components but not the intimacy component. This type of love can be exemplified by a whirlwind courtship and marriage in which a commitment is motivated largely by passion, without the stabilizing influence of intimacy. I recall one couple who went to a year high school reunion. Both of them had recently been divorced. After some drinks and dancing, they disappeared into a hotel room and never emerged to join in the rest of the weekend’s activities. Engulfed by passion, they got married a few days later. Then, after learning they had little in common and didn't really like each other, the marriage was annulled several months later. I call this type of relationship “The Hollywood Marriage.”
  

• Consummate Love is the only type of love that includes all three components--Intimacy, Passion and Commitment. Consummate love is the most complete form of love, and it represents the ideal love relationship for which many people strive but which apparently few achieve. Maintaining a consummate love relationship may be even harder than achieving it. The three components of love must be expressed in action for this form of love to flourish. I call this type of relationship “The Ideal Marriage.”