[Note: Anyone can contribute to this section as long as they keep their changes as reasonable as can be expected. Be sure to included media references and keep in mind this all speculative and not established fact.]

There are many different theories on zombies out there, and many times people end up debating whether or not they are capable of climbing stairs, or wether or not they run or not. This section is dedicated to the sorting and classification of different versions of zombies from every movie, book, TV show, game, etc....

Slow-Moving Zombies:

The Classic Zombie - The Classic Zombie had various nicknames including a "shambler" or a "crawler" due to the creature's slow pace and inability to run. Famously portrayed in the Romero series of films, these zombies appear to be suffering from rigor mortis; their movements are labored and stiff. They are many times portrayed to be dumb, slow-witted, with little or no ability to think and possessing limited sensed, rotting, and having a taste for human flesh (sometimes brains).

They have been portrayed in media to decay at various rates, but the true potential longevity of these type of zombies is truely unknown. It has been suggested that they may have the capacity for limited use of tools, such as using debris and objects as bludgeons, and may or may not be able to navigate a flight of stairs, or able to "mantle" mid sized objects (small boulders, waist high walls, general obstructions); although these remain speculative assertions at best. More so, there have also been unsubstantiated anecdotes that these creatures may attempt to re-enact common moments of their lives and to travel to a distinct, important location. It should be noted that there is no objective evidence of this.

Depending on the (currently unknown) vector of infection and incubation time, this condition can still potentially propagate just as effectively as as faster-moving, intelligent creature of the same capacity. Personal risk from these infected individuals is still extreme; they seem to possess superior stamina and comparable strength. They are of greatest threat in large numbers, in dense populations.

A true scientist would regard these as the only kind of true zombie; all other variations require some kind of food, which indicates that they require energy and water to operate, which is used to grow and regenerate, and most of them react and adapt to their environment very quickly, thus fulfilling many of the characteristics of being biologically alive. The most fundamental trait of a zombie is that it is undead, or biologically dead, but still animate, so therefore a creature ceases to be a "true" zombie if it requires food. All zombies try to eat, but "classic zombies" do not seem to use the nutrients for anything, and thus do not require energy, and thus do not grow or regenerate, and thus are medically dead.

Running Zombies:

Berserker - This classification of zombies is unique in the fact that they don't attempt to "infect" a survivor. They instead love to maim their targets, as if they just take pleasure from injuring a person. It is believed that the Adrenal glands are still functioning in this type of zombie, which allows it to reach a sprinting speed of up to 30 mph. They are partially intelligent in the fact that they have limited mimicry ability e.x.-say they see a person open a door with the handle, instead of knocking down the door they will use the handle to open it. They may choose to hide withing "mobs" of crawlers and then dead sprint when they spot a living.

Hunter - This classification of zombie belongs to both categories (Running, Intelligent). This is one of the few types of zombies that will operate alone and avoid other types of zombies. They are fast, stealthy, and incredibly cunning almost to the point of near human though in a predation mode. They prefer to stick to urban environments where they can hide in abandoned building and descend upon unsuspecting prey. Tall grass and wooded areas are also danger areas. Since their bodies are in full hunt mode muscle strength isn't as much as the "classic" zombie, they will go for the neck and other vital areas fast, two or three handgun rounds to the chest will drop them.

(all information here edited by Scout_Sergeant was taken from the zombie hunters comic series, full credit to the author.)

Intelligent Zombies:

Intelligent Classic Zombie - The notorious zombie film-maker George Romero famously depicted in his film, undead creatures who could emulate and copy human actions. The extent of this ability is questionable. Most zombies observed to be undertaking some kind of complicated action, appear to be totally unaware of their surroundings and their actions seem to be ideomotor and not intentional. Although there is a division, in both Land Of The Dead and the original Day of the Dead, there were zombie characters who were depicted to learn, either through necessity or being taught. Both characters, Bub (from Day of the Dead), and the zombie known as "Big Daddy" (from land of the dead) were able to successfully shoot a gun, think both strategically and mechanically, shown by their ability to reason and problem solve. Bub was depicted rather as a mindless dog-like creature, with an attachment to his master and who obeys simple commands with the offer of reward; near the end of the film he display self-motivation, but his final circumstances remain unknown. Alternatively, the character "Big Daddy" is portrayed as a zombie leader of sorts; other zombies seem to follow his example, as he leads them towards Fiddler's Green, solving problems as they are encountered. His basis for learning seems to be a very primal sense of self-preservation as opposed to being conditioned or taught.

Lich Zombie - These lesser-known pseudozombies are creations of David Wellington. Invoking either magic or undefined sci-fi, these creatures are cognitive beings, with full ability for language and thought. They have a limited capacity for fine dexterity and quickly loose touch with their humanity, as they require the consumption of life to exist. These creatures are few and far between in David Wellington's literary universe, and are vastly outnumbered by the generic "classic zombie", both being because caused by the same unseen force. These beings will decay and loose influence and power if they fail to feed, otherwise they will appear as a freshly-decease corpse, free of decay. Not only can these Lich Zombies wield weapons, armor and can think as well as any living human, but Lich Zombies commonly have supernatural powers of some form. These power vary greatly from individual to individual and their personal circumstances. These abilities range from invisibility, super strength, ESP, telekineses, projectile energy, psychoprojection, and much more. Although these Lich Zombie seem much more powerful, they have the same weakness as the classic zombie; the brain.

Zombie Subclasses:

Ankle Grabbers - These type of zombies will make life a LOT harder because they are the undead that have already been buried, but not decomposed enough to have no brain. these will ONLY appear in the case of a zombie out break "Night of the living dead" style, where you only have to die with your brain intact to become a Zombie. they don't appear in those cases 100% of the time, but if they do the amount of zombies will go up by at least 1/2( I'm not sure how long it would take for a intact corpse to decompose enough for the brain not to be salvageable by zombie-hood
so this number might be inaccurate.). That means that YOU SHOULDN'T HANG OUT IN A GRAVE YARD!!!! if you do they Will come up under you and either take you down underground or bite your ankles.(added by: Aerowolf)

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Note: Below is the new and better format, sorted by cause of zombification. Please use this from now on, and to move the information above into their proper classifications.
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"Voodoo" Zombies:

The "Voodoo Zombie" is best described as a zombie created by the means of an unknown/mystical force such as magic(Not necessarily Voodoo, but close enough). How they are able to function is many times unexplained, and overall, they are more or less a mystery.

In real life, a "Voodoo Zombie" will be found anywhere where there are large amounts of the religion known as voodoo being practiced. This creature is merely a human that has had the misfortune to befall a number of events

1. a drink or something is spiked by a voodoo person (i don't know the correct term, if you do put it here please).

2. because the chemical decreases life signs, the person is declared dead and buried.

3. the voodoo person digs up and revives the now brain damaged human

4. the now "voodoo zombie" is periodically administered a drug that forces the "voodoo zombie" to spend the rest of their life as a slave.

in short, a voodoo zombie is simply a brain damaged human under the influence of drugs, nothing mysterious at all.

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Viral/Infection Zombies:

One of the more popular/modern theories as to how zombies are formed, humans are infected by some sort of virus or a strain of very persistent bacteria while alive, or shortly after death. This causes the person to lose control of themselves, causing them to become cannibalistic or extremely violent. Not all 'zombies' in this category are technically "undead".

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Parasite Zombies:

Usually created by some sort of parasite, the human in question looses total control over their own body, and they may or may not still possess a brain. The parasite in question might have eaten the brain and hi-jacked the body's nerve system, or had plugged itself into the brain and hijacked the body from there, telling the brain what to do. Either way, a parasite zombie tends to be nothing more then a parasite with complete and total control over it's host.

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Psychological/Drug Zombies:

Technically not a zombie, but they are still considered a 'zombie'. They are normal humans who have been brainwashed, drugged, or both that go around killing non-humans...

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