A pontiff (from Latin pontifex) was, in Roman antiquity, a member of the most illustrious of the colleges of priests of the Roman religion, the College of Pontiffs. The term "pontiff" was later applied to any high or chief priest and, in Christian ecclesiastical usage, to a bishop and more particularly to the Bishop of Rome, the Pope or "Roman Pontiff".
The English term derives through Old French pontif from Latin pontifex, a word commonly held to come from the Latin root words pons (bridge) + facere (to do, to make), and so to have the literal meaning of "bridge-builder". This may be only a folk etymology, but it may also recall antique tasks and magic rites associated with bridges.
Ancient Rome 
There were four chief colleges of priests in ancient Rome, the most illustrious of which was that of the pontifices. The others were those of the augures, the quindecimviri sacris faciundis, and the epulones. The same person could be a member of more than one of these groups. Including the pontifex maximus, who was president of the college, there were originally three or five pontifices, but the number increased over the centuries, finally becoming 16 under Julius Caesar. By the third century B.C., the pontiffs had assumed control of the state religious system.
The word "pontiff", though now most often used in relation to a Pope, technically refers to any bishop. The phrase "Roman Pontiff" is not tautological, but means "Bishop of Rome", as "Alexandrian Pontiff" means Bishop of Alexandria. In the same way, the adjective "pontifical" does not refer exclusively to the Pope: a Pontifical Mass is a Mass celebrated by a bishop, not necessarily by a pope. From the adjective have been formed the nouns "the Pontifical" (the liturgical book containing the prayers and ceremonies for rites used by a bishop) and "pontificals" (the insignia of his order that a bishop uses when celebrating Pontifical Mass, not papal insignia, such as the papal tiara).
Other religions 
Inspiration for the Christian use of the name "pontiff" for a bishop could be found in the use of the same word (in Latin, pontifex, not "pontifex maximus") for the Jewish High Priest in the Vulgate Latin translation of the Scriptures, where it appears 59 times. For example, in the Vulgate Mark 15:11, "pontifices" (plural) is the Latin term used for "The Chief Priests", and in the Letter to the Hebrews "pontifex" (singular) is repeatedly used with reference to the Jewish High Priest and analogously to Jesus as the High Priest of Christians.
- "Pontifex". "Oxford English Dictionary", March 2007
- William Smith, A Dictionary of Greek and Roman Antiquities, article Pontifex, pp. 939-942
- Pontiff, The American Heritage Dictionary of the English Language
- In modern French the corresponding term is pontife
- Encyclopaedia Britannica, article Roman religion
- The Oxford Dictionary of the Christian Church (Oxford University Press 2005 ISBN 978-0-19-180190-3), article Pontifical
- The Oxford Dictionary of the Christian Church (Oxford University Press 2005 ISBN 978-0-19-180190-3), article pontificals
- Marcus 15:11