Aikido training is based primarily on two partners practicing pre-arranged forms (kata) rather than freestyle practice. The basic pattern is for the receiver of the technique (uke) to initiate an attack against the person who applies the technique—the 取り tori, or shite 仕手 (depending on aikido style), also referred to as 投げ nage (when applying a throwing technique), who neutralises this attack with an aikido technique.
Both halves of the technique, that of uke and that of nage, are considered essential to aikido training. Both are studying aikido principles of blending and adaptation. Nage learns to blend with and control attacking energy, while uke learns to become calm and flexible in the disadvantageous, off-balance positions in which nage places them. This "receiving" of the technique is called ukemi.Uke continuously seeks to regain balance and cover vulnerabilities (e.g., an exposed side), while nage uses position and timing to keep uke off-balance and vulnerable. In more advanced training, uke will sometimes apply reversal techniques (返し技 kaeshi-waza?) to regain balance and pin or throw nage.
Ukemi (受身?) refers to the act of receiving a technique. Good ukemi involves attention to the technique, the partner and the immediate environment—it is an active rather than a passive receiving of aikido. The fall itself is part of aikido, and is a way for the practitioner to receive, safely, what would otherwise be a devastating strike or throw.