Played by: Terry Farrell
Name before joining: unknown
Species: Trill (joined; 8th host of the Dax symbiont; listed as the 7th due to the purging of Joran Belar's joining from all official knowledge)
Position/occupation: Science officer, Deep Space Nine
Rank/title: Lieutenant until 4th season; Lt. Commander thereafter
Birthplace or childhood home: Trill
Parents: Kela (mother living as of 2372); father
Siblings: sister living as of 2372
Love interest(s): (before Worf) Deral; Captain Boday
Spouse: Worf (from "You Are Cordially Invited" until her death)
Hobbies/likes/interests: Jadzia enjoyed many foods and beverages from different cultures. Among them were steamed azna, Black Holes, and raktajino. Her leisure activities were likewise varied and multicultural. They included Klingon martial arts (she became an expert after joining), antigrav sailing, chess, poker, Galeo-Manada wrestling, and Tongo. Her favorite song was "All the Way".
Jadzia's entire early life was focused on becoming joined. After graduating from Starfleet Academy with premier distinctions in exobiology, zoology, astrophysics, and exoarchaeology, she went back to Trill and entered the inititate program, spending a difficult three years as a candidate. At that time, she was an extremely shy young woman. Then she was field evaluated by Curzon Dax, who made her life hell, and recommended that she be dropped. That was when Jadzia changed, becoming the first candidate to successfully reapply to the program, and was finally approved to receive a symbiont. When she heard that Curzon Dax was dying, she asked for the Dax symbiont, and was joined to it. She said later that she thought the irony appealed to Curzon.
In "Emissary", Jadzia Dax was assigned to DS9 as science officer, meeting Curzon's friend Benjamin Sisko, who was now her CO. She was the subject of an extradition hearing when Ilon Tandro tried to have her prosecuted for the betrayal and murder of his father, General Ardelon Tandro, which occurred when Dax was Curzon. Dax remained silent to protect the reputation of the general's widow, with whom Curzon had had an affair; but ultimately the widow came forward and provided an alibi ("Dax"). Later that year, Dax was faced with her doppelganger, who was Bashir's fantasy; she also imagined a subspace rift that seemed to threaten the station ("If Wishes Were Horses").
When a renegade Trill took over the station and demanded the Dax symbiont, Jadzia sacrificed herself to save her fellow officers, but the separation lasted only a few hours ("Invasive Procedures"). With Odo, she investigated a village in the Gamma Quadrant that turned out to be made up entirely of holograms ("Shadowplay"), and then she was placed in the role of field docent for the first time in her current host, to a young Trill candidate named Arjin ("Playing God"). In "Blood Oath", Dax was reunited with three old Klingon friends of Curzon's, with whom Curzon had sworn a blood oath to kill a pirate called the Albino. Though she was released from the oath, she was determined to participate, and did so.
In "Equilibrium", Dax began suffering life-threatening hallucinations which turned out to be emerging memories of Joran, a previously forgotten past host. The memories were finally allowed to be integrated. Dax later fell in love with Deral, an inhabitant of a planet that faded in and out of corporeality. She was prepared to go noncorporeal too to be with him, but this proved impossible ("Meridian"). In "Past Tense, Parts I and II", Dax was stranded in 2024 San Francisco with Sisko and Bashir; and in "Facets", she "met" her previous hosts, embodied by other DS9 personnel, in her long-delayed zhian'tara. Curzon, hosted by Odo, admitted that he had washed Jadzia out because he was in love with her.
Dax received a promotion sometime between "The Adversary" and "The Way of the Warrior". In "Rejoined", she was reunited with Lenara Kahn, current host of a symbiont once borne by the wife of Torias Dax, and their old love resurfaced. Dax was willing to face exile to be with Lenara, but Lenara chose to leave. Dax later accompanied Kor and Worf on a quest for a famed Klingon artifact ("The Sword of Kahless"); and she aided Bashir in fighting the Blight in "The Quickening".
It was in "Looking for Par'Mach in All the Wrong Places" that Dax declared her feelings for Worf, and they became romantically involved; they went to Risa together in "Let He Who is Without Sin...". Dax, along with Sisko and Garak, was involved in Odo's telepathic flashback to his tenure under the Cardassians ("Things Past"); and she went along on Worf and Martok's mission on the Rotarran in "Soldiers of the Empire".
Dax evacuated DS9 with the other Starfleet officers in "Call to Arms", after promising Worf that she would marry him after the war. In "Behind the Lines", she captained the Defiant when Sisko was made Admiral Ross' adjutant, and in "Favor the Bold"/"Sacrifice of Angels", she returned to the station with Sisko.
Shortly thereafter, in "You Are Cordially Invited", Dax and Worf were married, although the union was opposed at first by Martok's wife Sirella. Later, on a mission with Worf to aid the defection of a Cardassian informant, Dax was critically injured, but Worf chose her over the mission ("Change of Heart").
In "Tears of the Prophets", Dax and Worf were in the early stages of planning to have a baby when he left on the Defiant's mission to Chin'toka. Dax was in the Bajoran shrine with the Orb of Contemplation when Dukat beamed in, possessed by a pah-wraith which blasted her with energy. Jadzia was mortally injured and died later in the infirmary, although the Dax symbiont was saved.
Other facts: Jadzia was right-handed, and also slightly acrophobic (a legacy of Curzon, who once fell out of a tree). She was the only one in her family to be joined.