This article is about Death in general. For a list of deaths that occurred throughout the Final Destination series, see here.
In the strictest sense, Death is simply the temporary or permanent cessation of any and all biological functions that sustains a living organism. Though in the context of the Final Destination series, Death is an active, ominipotent, cunning, volatile, highly malevolent, supernatural entity and the series' primary antagonist. While not visible to the human eye, it nevertheless makes a somewhat noticable and ominous prescence wherever it goes and can manipulate any aspect of an environment to it's will.
It has been suggested that Death essentially programs the events of a person's entire lifespan, deciding where, when and how they will die. Should anyone deviate or "cheat" from what Death has set for them, whether deliberately or not, Death becomes infuriated and eventually returns for them, usually in the worst, most painful way imaginable. Because of this, suicide is pratically moot unless that is what Death had ultimately planned for them. Any attempt to cheat is ultimately futile as it's implied that Death maintains an agenda of some kind in order to keep forces of life and death balanced and will meet that quota one way or another.
The Final Destination Series
Throughout the series, Death comes in the form of overly complex freak accidents to kill off the survivors of a major disaster they were originally supposed to die in as well as in the order they would have died in said disaster. If somebody intervenes in a person's death, then Death would skip that person and move on to the next before returning to that person to complete the rift in its design, although the order has been shown to reverse itself in Final Destination 2.
There are also a few cases where someone's death comes before (or after) another victim on the list for an unexplained reason (Gunter Nonhoff and Eric Prescott most notably). Death will, however, seemingly make implausible situations when someone deliberately trying to commit suicide wlll ultimately fail, as seen when Eugene Dix tries to shoot himself in the head with a six shot revolver, only for every bullet to be a misfire.
Ususally there are mysterious clues as to how the next person will die, it's most common form being a brief gust of spontaneous wind. Other secondary clues range from pictures or brief images or signs or an odd formation of something on the ground.
The clues could be about anything on how they die (i.e. the word "EYE" for Evan Lewis, a series of cracks in the ground that look like a skeletal hand for Hal Ward, the song "Rocky Mountain High" for various situations, or nothing but a dark, black shadow that appears out of nowhere).
Death also has a handful of servants who unintentionally (in some cases on purpose) kill a person next on Death's list. Additionally, Death does not appear to be above killing others to hasten its acquisition of survivors, with Tom Gaines theorizing the entity is perfectly willing to "sneak souls" when the opportunity to do so arises.
There have been mixed theories in what Death will do if the survivor with premonitions deliberately kills him/herself despite not being next on the list. Ian had a theory that, if the last in Death's list (the premonitionist) kills himself, It would ruin death's plans, since the survivor isn't next to die.
It would throw Death's list away and save everyone else still alive from the accident. In an alternate ending in The Final Destination, Nick kills himself, ruining Death's design. However, at the very end of it, the final two survivors of the McKinley Speedway accident died at the exact same moment, meaning Death will just kill the rest of the survivors without hesitation based on the design they were supposed to die.
In the alternate ending of Final Destination, Alex saves Clear from an electric wire on the front of the car, therefore, he was caught on fire, and died ruining Death's design. After this, Clear and Carter both lived the rest of their lives in peace, meaning that the final survivors of Flight 180 actually defeated Death. It was not clear on what Death will actually do if this situation happened, since these situations only happened in alternate endings.
It should be noted however that in Final Destination 3 it took five months after Ian's death for Train 081 to happen meaning that in the alternate ending of Final Destination the reason Clear and Carter survived is because the scene showed could have been before five months passed or because Clear gave birth to a baby, as it was mentioned in Final Destination 2 that if someone who was supposed to die in an accident but survived and gave birth all the remaining survivors would live, William Bludworth himself said that "only new life defeats Death".
Death takes many forms (skulls, shadows, possessed objects that ultimately kill their victims) but his most notable form (which was in the novel Final Destination: Looks Could Kill) was an elderly African American male who wears a gray suit, has shiny white teeth, gray hair, and a cane with a skull on the end; Death adopts a form similar to this one in a dream Kate Shelley has in Final Destination: End of the Line, implicating it may be its preferred one when dealing directly with mortals. However, Death being written off as a skeleton with a black cape and scythe is merely a stereotype (The Grim Reaper).
Death's true form (according to a dream Jessica Golden and Macy had in Final Destination: Dead Reckoning) could possibly be a massive abomination composed of decaying, shifting corpses and bones from thousands of species. Also in Final Destination: Spring Break, Death can be seen as a giant cloud of smoke. In the Final Destination film series, Death is never physically shown but it's presence is known when there is a sudden large gust of wind or when it casts a large, dark shadow.