A romantic relationship is one where you have a deep feeling of connection to the other person. All systems are go. You accept them as they are, want them to feel good, and deeply appreciate who they are. And vice versa. One of the ways you desire to express your love for them through your sexuality.
Sex is the one key element that distinguishes a romantic relationship from all other types.
There are some feelings we have when infatuated that we don't have when we're feeling love. When infatuated, we are thrilled, but not happy, wanting to trust, yet suspicious. We're miserable when they're away, almost like we're not complete unless we're with them. It's a rush and it's intense. It's difficult to concentrate.