Sōke 宗家, is a Japanese term that means “the head family and is mainly used in Japanese traditional arts. Thus, it is often used to indicate “headmaster” (or sometimes translated as “head of the family” or even “grand master” but only rarely and mostly incorrectly used.) The English translation of sōke as “grand master” is not a literal translation but it does see use by some Japanese martial arts references.
It cannot mean one who is the leader of any school, but is used for the head master of a style, but it is most commonly used as a highest level Japanese title, referring to the singular leader of a school or style of martial art. The term, however is controversial in that its use in Japan was small until western founders began using it in relation to their arts and systems in the nineteen seventies and early eighties.
Sōke is sometimes mistakenly believed to mean “founder of a style” because many modern sōke are the first generation headmasters of their art (shodai sōke), and are thus both sōke and founder. However, the successors to the shodai sōke are also sōke themselves. Sōke are generally considered the ultimate authority within their art, and have final discretion and authority regarding promotions, curriculum, doctrine, and disciplinary actions. A sōke has the authority to issue a menkyo kaidencertificate indicating that someone has mastered all aspects of his style. It is considered the highest form of Soke are the inheritors of an old system, usually with letters and documentation to the fact of lineage.
In some schools such as Kashima-Shinryuthere is a related position called Shihanke(師範家 hiragana: しはんけmeaning “Instructor Line” that fills a very similar role. A Shihanke is essentially a second training lineage that exists autonomously from the Sōke. In arts where there is a Shihanke and a Sōke it is possible for the position of Sōke to essentially be a hereditary honorary title in the Iemoto system while the Shihanke is responsible for the actual teaching and operation of the school.