Aiki, a Japanese budō term, at its most basic is a principle that allows a conditioned practitioner to negate or redirect an opponent's power.

However, care must be taken about the absolute meanings of words when discussing concepts derived from other cultures and expressed in different languages.

This is particularly true when the words we use today have been derived from symbols, in this case, Japanese kanji, which represent ideas rather than literal translations of the components.

Historically, the principle of aiki would be primarily transmitted orally, as such teachings were often a closely guarded secret.

In modern times, the description of the concept varies from the physical[1] to vague and open-ended, or more concerned with spiritual aspects.

Aiki is an important principle in several other arts such as Kito-ryu, Judo, Yamabujin Goshin jutsu and various forms of Kenjutsu and Japanese Jujutsu.

Culturally, and due to certain necessities of the time period, the aiki knowledge was usually a very well-guarded secret and rarely disclosed.