Aiki (martial arts principle) and its practice is often kept within a particular individual or two from a family/school lineage. Culturally, and due to certain necessities of the time period, the aiki knowledge was usually a very well guarded secret and rarely disclosed. The oldest book to have historically discuss aiki was the 1899 Budo Hiketsu-Aiki no Jutsu. On the subject of aiki it was written: The Textbook of Jujutsu (Jujutsu Kyoju-sho Ryu no Maki) from 1913 wrote: Aiki (martial arts principle) Aiki from a Japanese budo term, at its most basic is a principle that allows a conditioned practitioner to negate or redirect
Japanese particles (written using a hiragana character with no other use in modern Japanese, originally assigned as "wo", now usually pronounced "o", though some speakers render it as "wo"). These exceptions are a relic of historical kana usage. There are eight types of particles, depending on what function they serve. Note that some particles appear in two types. For example, ""kara"" is a "case marker" where it describes where something is from or what happens after something; when it describes a cause it is a "conjunctive particle". "Ni" and "de" can both be used to show location, corresponding to the prepositions "in"