The word "mecha" (メカ, meka) is an abbreviation, first used in Japanese, of the word "mechanical". In Japanese, mecha encompasses all mechanical objects, including cars, guns, computers, and other devices, and the term "robot" (ロボット, robotto) or "giant robot" is used to distinguish limbed vehicles from other mechanical devices. Outside of this usage, it has become associated with large humanoid machines with limbs or other biological characteristics. Mechas differ from robots in that they are piloted from a cockpit, typically located in the chest or head of the mech.
While the distinction is often hazy, mecha typically does not refer to form-fitting powered armor such as Iron Man's suit. They are usually much larger than the wearer, like Iron Man's enemy the Iron Monger, or the mobile suits depicted in the Gundam series.
In most cases, mecha are depicted as fighting machines, whose appeal comes from the combination of potent weaponry with a more stylish combat technique than a mere vehicle. Often, they are the primary means of combat, with conflicts sometimes being decided through gladiatorial matches. Other works represent mecha as one component of an integrated military force, supported by and fighting alongside tanks, fighter aircraft, and infantry, functioning as a mechanical cavalry. The applications often highlight the theoretical usefulness of such a device, combining a tank's resilience and firepower with infantry's ability to cross unstable terrain and a high degree of customization. In some continuities, special scenarios are constructed to make mecha more viable than current-day status. For example, in Gundam the fictional Minovsky particle inhibits the use of radar, making long-range ballistic strikes impractical, thus favouring relatively close range warfare of Mobile Suits.
However, some stories, such as the manga/anime series Patlabor and the American wargame BattleTech universe, also encompass mecha used for civilian purposes such as heavy construction work, police functions or firefighting. Mecha also see roles as transporters, recreation, advanced hazmat suits and other R and D applications.
Mecha have been used in fantasy settings, for example in the anime series Aura Battler Dunbine, The Vision of Escaflowne, Panzer World Galient and Maze. In those cases, the mecha designs are usually based on some alternative or "lost" science-fiction technology from ancient times. In case of anime series Zoids, the machines resemble dinosaurs and animals, and have been shown to evolve from native metallic organisms.
A chicken walker is a fictional type of bipedal robot or mecha, distinguished by its rear-facing knee joint. This type of articulation resembles a bird's legs, hence the name. However, birds actually have forward-facing knees; they are digitigrade, and what most call the "knee" is actually the ankle.