Mecha

Mecha are the giant robots of science fiction: typically humanoid walking machines, either piloted or sentient, and distinct from autonomous robots because a person rides along, usually in a cockpit in the chest or head. The word is a Japanese abbreviation of "mechanical", and the genre's two traditions split early: super robot stories feature one-of-a-kind machines with mystical or exotic power sources, often piloted by teenagers, while real robot stories, established by Mobile Suit Gundam in 1979, treat mecha as mass-produced military hardware fielded alongside tanks, aircraft and infantry.

For a novelist the genre is a constraints problem: the real-robot branch runs on grounded logic (see hard vs soft science fiction), and every machine's specifications, faction and fuel is canon a long series must keep straight. In scale it is a sibling of space opera.