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The formal Techniques (Waza) of Judo are described by the original governing body of Judo (The Kodokan) as:
Nage-Waza : Throwing Techniques (67)
-Te-Waza : Hand-Throwing-Techniques (15)
-Koshi-Waza : Hip Throwing-Techniques (11)
-Ashi-waza : Foot/Leg Throwing-Techniques (21)
-Masutemi-Waza : Straight/Back Sacrifice Techniques (5)
-Yokosutemi-Waza : Side Sacrifice Techniques (15)
Katame-Waza : Ground Grappling Techniques (29)
-Osaekomi-Waza : Holding Techniques (7)
-Shime-Waza : Choking Techniques (12)
-Kansetsu-Waza : Joint-Locking Techniques (10)
In addition there are many more variations, combinations, transitional, controlling and hybrid, competition-proven techniques.
A Judoka many spend many years practising and studying, and hope to master only a handful of these techniques.
If the the throws don't work to maximum effect, the Judoka must attempt to gain victory on the ground. One standard path to victory is to hold the opponent down. Equally the Judoka must learn to escape these holds (Nige-Waza)