Human domestic partners
A partner was anyone who entered into a partnership with another person, whether being a business partnership such as a sidekick; or a domestic partnership, such as marriage mates or sexual partners, such as boyfriends or girlfriends. (DIS: "Context Is for Kings")
In the 22nd century, Charles Tucker III liked to take his girlfriend to Chatkin Point to stare at the moon in his car, which he parked along the shoreline. (ENT: "Precious Cargo")
In 2256, when Paul Stamets was behaving strangely due to his experience with the spore drive, Doctor Hugh Culber told Tyler and Burnham to excuse his partner, as he hadn't been himself lately. (DIS: "Magic to Make the Sanest Man Go Mad")
In 2266, Benton and Gossett were the business partners of Ben Childress. They worked as lonely miners on Rigel XII and were the victims of Harry Mudd's con job. (TOS: "Mudd's Women")
When he heard that Wesley Crusher couldn't dance, Data offered to give him dance lessons. He had created a comprehensive seventeen-part course with some "interesting holographic dancing partners". (TNG: "The Game")
When Quark was chosen to conduct negotiations for acquisition of tulaberry wine with the Dosi in 2370, it was suggested that he may need someone to work with him to take the blame of a potential failure. At first Rom suggested that he be chosen as a consultant help him, however, Quark instead chose Pel, not as a partner, but as an assistant, at the agreed rate of 20 percent of the profits. (DS9: "Rules of Acquisition")