Nilani Kahn was a joined Trill and a host of the Kahn symbiont in the 23rd century. She was married to Torias Dax, though Torias was killed in 2285 in a shuttlecraft accident only a few months after he was joined. After she died, the Kahn symbiont was joined to Lenara.
Kahn wanted to study theoretical quantum physics. She later recalled that Torias's eyes always glazed over the moment she brought up this discussion.
Kahn and Dax were reunited in 2372 as Lenara and Jadzia. Jadzia told Lenara that Torias knew the shuttle was not ready for a full impulse test but he proceeded anyway, and that he was sorry for leaving Nilani alone. (DS9: "Rejoined")