Judo (柔道, jūdō?), meaning "gentle way", is a modern Japanese martial art (gendai budō) and combat sport, that originated in Japan in the late nineteenth century. Its most prominent feature is its competitive element, where the object is to either throw one's opponent to the ground, immobilize or otherwise subdue one's opponent with a grappling maneuver, or force an opponent to submit by joint locking the elbow or by executing a choke. Strikes and thrusts (by hands and feet)—as well as weapons defences—are a part of judo, but only in pre-arranged forms (kata) and are not allowed in judo competition or free practice (randori).
Ultimately, the philosophy and subsequent pedagogy developed for judo became the model for almost all modern Japanese martial arts that developed from "traditional" schools (koryū). In addition, the worldwide spread of judo has led to the development of a number of offshoots such as Sambo and Brazilian Jiu Jitsu. Practitioners of judo are called jūdōka.
While judo includes a variety of rolls, falls, throws, hold downs, chokes, joint-locks, and strikes, the primary focus is on throwing (投げ技, nage-waza?), and groundwork (ne-waza). Throws are divided in two groups of techniques, standing techniques (tachi-waza), and sacrifice techniques (捨身技, sutemi-waza?). Standing techniques are further divided into hand techniques (手技, te-waza?), hip techniques (腰技, koshi-waza?), and foot and leg techniques (足技, ashi-waza?). Sacrifice techniques are divided into those in which the thrower falls directly backwards (真捨身技, ma-sutemi-waza?), and those in which he falls onto his side (橫捨身技, yoko-sutemi-waza?).
The ground fighting techniques (ne-waza) are divided into attacks against the joints or joint locks (関節技, kansetsu-waza?), strangleholds or chokeholds (絞技, shime-waza?), and holding or pinning techniques (押込技, osaekomi-waza?).
A kind of sparring is practiced in judo, known as randori (乱取り?), meaning "free practice". In randori, two adversaries may attack each other with any judo throw or grappling technique. Striking techniques (atemi-waza) such as kicking and punching, along with knife and sword techniques are retained in the kata. This form of pedagogy is usually reserved for higher ranking practitioners (for instance, in the kime-no-kata), but are forbidden in contest, and usually prohibited in randori for reasons of safety. Also for reasons of safety, chokeholds, joint locking, and the sacrifice techniques are subject to age or rank restrictions. For example, in the United States one must be 13 or older to use chokeholds, and 16 or older to use armlocks.
In randori and tournament (shiai) practice, when an opponent successfully executes a chokehold or joint lock, one submits, or "taps out", by tapping the mat or one's opponent at least twice in a manner that clearly indicates the submission. When this occurs the match is over, the tapping player has lost, and the chokehold or joint lock ceases.