In science fiction, mecha or mechs are giant robots or machines controlled by people, typically depicted as humanoid walking vehicles. The term was first used in Japanese after shortening the English loanword 'mechanism' or 'mechanical', but the meaning in Japanese is more inclusive, and 'robot' or 'giant robot' is the narrower term.
Fictional mecha vary greatly in size and shape, but are distinguished from vehicles by their humanoid or biomorphic appearance, although they are bigger, often much bigger, than human beings. Different subgenres exist, with varying connotations of realism. The concept of Super Robot and Real Robot are two such examples found in Japanese anime and manga.
Real-world piloted humanoid or non-humanoid robotic platforms, existing or planned, may also be called "mecha". In Japanese, "mecha" may refer to mobile machinery or vehicles (including aircraft) in general, piloted or otherwise.
'Mecha' is an abbreviation, first used in Japanese, of 'mechanical'. In Japanese, mecha encompasses all mechanical objects, including cars, guns, computers, and other devices, and 'robot' 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 franchise.
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.