Romance
"Did your skin ever flush when you were near another person? Did your stomach ever feel like someone hollowed it out with a knife when you were apart? Did your throat ever swell when you realised it was over? Seven of Nine, Seven of Nine told me love's like a disease. Well, maybe it is. Pheromones, endorphins, chemicals in our blood, changing our responses, physical discomfort, but any way you look at it, it's still love."
Romance, romantic love, or being in love was a strong feeling of love, attraction, and emotional attachment to another individual. Something which evoked the feeling of romance was also said to be romantic. A romantic relationship was a type of interpersonal relationship. Romantic love contrasted with platonic love.
In 1930, time traveler Captain James T. Kirk believed he was in love with Edith Keeler who had to die to restore the altered timeline. (TOS: "The City on the Edge of Forever")
In 2263 of the alternate reality, Nyota Uhura was surprised to see Spock at James T. Kirk's birthday party, as she thought he had a mission report to complete. He confirmed that he did, adding that he thought it would be "more pleasing to engage with you socially." Touched, she replied, "You old romantic." (Star Trek Beyond)
In 2266, Communications Officer Nyota Uhura stated she was an illogical woman who was beginning to feel too much a part of her communications console and asked Spock why he didn't ask if she'd ever been in love. Later, Doctor Leonard McCoy admitted that he may have been looking at who he thought to be Nancy Crater through a romantic haze as she looked just as he'd known her ten years before. (TOS: "The Man Trap")
In 2375, Derran Tal, a Varro, thought it was romantic that her making love with the Human Harry Kim was a breach in protocol. Seven of Nine noted romantic love as an attraction based on sexual desire when it facilitated procreation. Seven also noted that the Borg had referenced romantic love in over six thousand assimilated species. Kim later disobeyed Captain Kathryn Janeway's orders because he and Tal were in love. Seven had assumed that romantic love was a Human weakness, but saw that it could also be a source of strength. (VOY: "The Disease")