Aiki 合氣 is the joining or combining of energy.

Techniques are accomplished with subtlety and require little mechanical force. Emphasis is upon blending with the the opponent to redirect the force of the attack rather than opposing it head on.

Aiki is about engaging an attack, not retreating from it. One applies aiki by understanding the rhythm and intent of the attacker to find the optimal position and timing to apply a counter technique.

Aiki martial arts styles incorporate weapons techniques such as the sword and stick, as well as empty hand strikes, kicks, projections, strangulations, dislocations, and immobilizations.

The aiki arts share many similarities with much of their differences coming in the way they are taught, organized, and applied.