Self-sacrifice was the giving up of one's own life to benefit others. In this way it differed from suicide.

The Eighth Doctor believed that his life was the only one he had the right to sacrifice. Though he would not sacrifice his fellow passengers on the rocket from Deimos to ensure the survival of a greater number in peril on Mars, he was willing to put his own life on the line. (AUDIO: The Resurrection of Mars)

Daleks believed that self-sacrifice was impossible because it was not logical. (TV: Destiny of the Daleks) Despite this, Daleks often sacrificed themselves for the cause of conquest. (COMIC: The Amaryll Challenge, The Menace of the Monstrons, PROSE: Mission to Galacton)

In the early days of Skaro, the humanoid Dalek Lodian sacrificed himself by by blowing up his ship in order to kill Zet before he could tell the new Daleks the location of Earth. (COMIC: Legacy of Yesteryear)

In 1870, Kahler-Jex sacrificed himself in order to prevent Kahler-Tek from killing any more people or races who would get caught in the crossfire of Tek's hunt for Jex if Jex were to escape to another world. (TV: A Town Called Mercy)

In 2007, Ursula Blake, Colin Skinner, Bridget Sinclair and Bliss, having access to the Abzorbaloff's thoughts after being absorbed by him, strained against his flesh, causing him to drop his cane. On Ursula's instruction, Elton Pope broke the cane, causing the Abzorbaloff to himself be absorbed by the Earth, dissolving along with his victims. Soon after, however, Ursula was partially restored by the Tenth Doctor's sonic screwdriver. (TV: Love & Monsters)

In 2008, during the Sontaran invasion of Earth, the Tenth Doctor threatened to ignite an atmospheric converter aboard the Sontaran flagship. However, his place was taken via teleport by Luke Rattigan, who ignited the device himself, destroying the ship with himself onboard. (TV: The Poison Sky)

A Donna Noble from a parallel world sacrificed herself by walking in front of a lorry to create a traffic jam that would force her past self to reconsider the decision that would led to the death of the Tenth Doctor in the parallel world. (TV: Turn Left)

The Tenth Doctor took Wilfred Mott's place in a glass booth where he received a fatal dose of radiation which ultimately resulted in his regeneration into the Eleventh Doctor. (TV: The End of Time) In an alternate timeline, however, he decided against self-sacrifice and so left Wilf to die. (COMIC: Four Doctors)

In 2020, Rory Williams took a blast from a sonic disc fired at the Eleventh Doctor by Restac. (TV: Cold Blood)

In 2050, K9 Mark I, after ensuring that Alistair Gryffen, Jorjie Turner and Starkey left the area, initiated self-destruct to stop four Jixen warriors within Gryffen Manor. Soon after, his regeneration unit regenerated him into the form of K9 Mark 2. (TV: Regeneration) As Starkey would later recall, "he gave his life... his previous life to save us." (TV: The Bounty Hunter)

In 2059, Adelaide Brooke sacrificed herself to restore the timeline after the Tenth Doctor altered it to save the crew of Bowie Base One. (TV: The Waters of Mars)

On Midnight, a Crusader 50 hostess sacrificed herself to save her passengers from the Midnight entity by throwing herself and the entity's host out the shuttle bus doors onto the surface of Midnight, exposing them both to the extreme X-tonic radiation outside. (TV: Midnight)

In the 42nd century, Kath McDonnell sacrificed herself by jumping out of the airlock of the SS Pentallian, dragging her possessed husband with her, in order to save the ship's crew from the revenge-seeking, sentient Torajii star. (TV: 42)

In the 51st century, the Tenth Doctor was prepared to hook himself up to the computer of the Library in order to free the people within, which have killed him beyond regeneration. However, his place was taken by River Song, who knew the Doctor in his future. Thanks to a neural relay provided by the future Doctor, River lived on within the Data Core. (TV: Forest of the Dead)

In 6012, Jenny took an apparently fatal gunshot wound intended for the Tenth Doctor by General Cobb. (TV: The Doctor's Daughter)

In 200,100, after Rose Tyler absorbed vortex energy from the heart of the TARDIS, the Ninth Doctor in turn absorbed the energy from her via a kiss in order to save her life. As a result, he regenerated into the Tenth Doctor. (TV: The Parting of the Ways)

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