A
substitute teacher is a person who
teaches a
school class when the regular teacher is unavailable; e.g., because of illness, personal leave, or other reasons. "Substitute teacher" (usually abbreviated as "sub") is the most commonly used phrase in the
United States,
Canada,
India and
Ireland, while
supply teacher is the most commonly used term in
Great Britain and the Canadian
province of
Ontario. Common synonyms for substitute teacher include
relief teacher or
casual teacher (used in
Australia and
New Zealand) and "emergency teacher" (used in the
United States). Other terms, such as "guest teacher", are also used by some schools or districts. Regional variants in terminology are common, such as the use of the term
teacher on call (
T.O.C.) in the Canadian
province of
British Columbia and
occasional in Ontario.