Cantuar is a title

Title

A title is a prefix or suffix added to someone's name to signify either veneration, an official position or a professional or academic qualification. In some languages, titles may even be inserted between a first and last name...

 that the Archbishop of Canterbury

Archbishop of Canterbury

The Archbishop of Canterbury is the senior bishop and principal leader of the Church of England, the symbolic head of the worldwide Anglican Communion, and the diocesan bishop of the Diocese of Canterbury. In his role as head of the Anglican Communion, the archbishop leads the third largest group...

 is legally permitted, in England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

, to use to sign his name as a substitute for the surname

Surname

A surname is a name added to a given name and is part of a personal name. In many cases, a surname is a family name. Many dictionaries define "surname" as a synonym of "family name"...

.

He shares the right to use only a title in the signature with the Archbishop of York

Archbishop of York

The Archbishop of York is a high-ranking cleric in the Church of England, second only to the Archbishop of Canterbury. He is the diocesan bishop of the Diocese of York and metropolitan of the Province of York, which covers the northern portion of England as well as the Isle of Man...

, other English bishop

Bishop

A bishop is an ordained or consecrated member of the Christian clergy who is generally entrusted with a position of authority and oversight. Within the Catholic Church, Eastern Orthodox, Oriental Orthodox Churches, in the Assyrian Church of the East, in the Independent Catholic Churches, and in the...

s, and Peers of the Realm. The archbishop of York is known as "Ebor", from the Roman name for York: Eboracum.

"Cantuar." is also used a Latin abbreviation for the University of Kent

University of Kent

The University of Kent, previously the University of Kent at Canterbury, is a public research university based in Kent, United Kingdom...

 (formerly the "University of Kent at Canterbury") in England and for the University of Canterbury

University of Canterbury

The University of Canterbury , New Zealand's second-oldest university, operates its main campus in the suburb of Ilam in the city of Christchurch, New Zealand...

 (Christchurch, New Zealand) which also uses a shortened version of the abbreviation ("Cant.").

Cantuar is a named place in Saskatchewan

Saskatchewan

Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota....

, Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

.