Jadzia Dax was a joined Trill, the eighth host of the Dax symbiont from 2367 to 2374, and a Starfleet officer. She was born in 2341 on the Trill homeworld and was joined to Dax in 2367 after the death of its previous host, Curzon.
Growing up, Jadzia was always a shy and quiet child. She lived with her mother, father and sister on Trill and was always very driven by her ambitions to one day be joined to a symbiont. She spent much of her early life focusing on achieving her goals. She was the only member of her family who would ever become joined to a symbiont.
(DS9: "Invasive Procedures")

Prior to her joining, Jadzia attended Starfleet Academy and applied to the Trill Symbiosis Commission for joining after graduation. While at the Academy, she gained degrees in astrophysics, exoarchaeology, exobiology, and zoology.
(DS9: "Playing God")

After working hard, Jadzia was initially rejected for joining and eliminated from the program by her field docent, Curzon Dax in 2364. She successfully re-applied that same year and became the only Trill in history to successfully complete the program after having been rejected.
(DS9: "Equilibrium")

This experience would haunt her for years to come and is a reason why she never had positive feelings about returning to Trill. She never could understand why she was washed out of the program by Curzon.

After being approved for joining, she heard of Curzon's deteriorating health and requested that she receive the Dax symbiont after he died. She was joined to Dax in 2367. Later, during her zhian'tara, she learned that Curzon's reasons for rejecting her original application were personal, and that he had actually been in love with her.
(DS9: "Facets")

After being joined to Dax, Jadzia's training and experiences made the adjustment to having six different lifetimes of memories and experiences relatively easy. The once shy, hardworking and dedicated Jadzia became a lively, confident and outgoing person, with a passion for life.

Even as an ensign and lieutenant jg in Starfleet, she had dealings with many prominent officers. She was acquainted with Captain Keogh, though the two did not get along. She was also friends with Captain Shelby, who even owed her a favor, which Jadzia eventually cashed in.
(DS9: "The Jem'Hadar", "You Are Cordially Invited")

Twenty-eight-year-old Lieutenant Jadzia Dax was assigned as science officer aboard the space station Deep Space 9 in 2369 under the command of Benjamin Sisko, who had been a friend of Curzon.
(DS9: "Emissary")

In 2370, the Dax symbiont was removed from Jadzia and kidnapped by an unjoined Trill, Verad.
(DS9: "Invasive Procedures")

Jadzia kept an oath made by Curzon with his Klingon brothers. His friends' sons had been killed by the Albino, a master criminal, and they vowed vengeance.
(DS9: "Blood Oath")

Jadzia was threatened with the removal of Dax a second time in 2371, when it was discovered that a previously undisclosed host, Joran Belar, had been psychotic.
(DS9: "Equilibrium")

Sometime between stardates 48959 and 49011 Jadzia was promoted to Lieutenant Commander.

Jadzia joined Worf on Martok's ship, the IKS Rotarran. The crew was lax and had no fighting spirit due to the constant defeats by the Jem'Hadar. She helped instill Klingon pride and spirit in them, and they won their first battle.
(DS9: "Soldiers of the Empire")

After Deep Space 9 was taken by the Cardassian/Dominion fleet, Jadzia piloted the Defiant to safety.

During a mission to destroy a ketracel-white facility in Cardassian space, the Dax symbiont was badly injured.

Jadzia was given command of the Defiant in early 2374 by Admiral Ross after promoting Captain Sisko to be his adjutant.

She was aboard the Defiant for Operation Return and was present for Sisko's near-suicide mission into the wormhole to stop Dominion reinforcements from coming through.
(DS9: "Call to Arms", "A Time to Stand", "Favor the Bold")

When the Federation and allied forces went on the offensive at the First Battle of Chin'toka, she stayed behind and took command of the Deep Space 9. Sadly, though, while her crewmates were fighting the battle, Gul Dukat (controlled by a Pah-wraith) struck her down.
(DS9: "Tears of the Prophets", "Shadows and Symbols")

Jadzia was an outgoing individual with varied interests. Many of her pursuits were the result of influences from her previous hosts. Joran Dax left her with an appreciation for music, even though no one in her family had any musical ability, and after re-integrating Joran's personality she regularly practiced playing music herself.
(DS9: "Equilibrium", "Facets", "Playing God")

Her favorite song was "All the Way."
(DS9: "Image in the Sand")