Glossary of Terms: O
- O Antiphons
- OC
- OI
- Oakerhater, David Pendleton
- Oath of Allegiance
- Oath
- Oath
- Oblate
- Oblation
- Oblation
- Obsecrations
- Obsequies
- Occasional Offices
- Occasional Papers of the Standing Liturgical Commission, The
- Occurrence
- Octave
- Odium Theologicum
- Oertel, Johannes Adam Simon
- Offering, Offerings
- Offertory, Offertory Procession, Offertory Sentence
- Office Hymn
- Office of Institution
- Officiant
- Oglethorpe, James Edward
- Ohio, Diocese of
- Oil Stock
- Oil, Holy
- Oil, Holy
- Oil, Holy
- Okalona College
- Okinawa, Missionary District of
- Oklahoma, Diocese of
- Old North Church, Boston
- Old Swede's Church, Wilmington, Delaware
- Old Testament
- Olney Hymns
- Olympia, Diocese of
- Onderdonk, Benjamin Tredwell
- Onderdonk, Henry Ustick
- Ontology
- Open Communion
- Open Pulpit, Canon on
- Open Pulpit
- Opening Acclamation
- Opening Preces
- Opening Sentences
- Open
- Orans Position
- Oratory
- Order of Service for Noonday, An
- Order of Worship for the Evening, An
- Order of Worship for the Evening, An
- Order of Worship for the Evening, An
- Orders, Holy
- Order
- Order
- Order
- Ordinal, The
- Ordinand
- Ordinary (of a diocese)
- Ordinary Time
- Ordination of Women
- Ordination
- Ordination
- Ordination
- Oregon and Washington, Missionary District of
- Oregon, Diocese of
- Original Sin
- Original Sin
- Original Sin
- Original Sin
- Orison
- Ornaments Rubric, The
- Ornaments, Church
- Orphrey
- Osculatorium
- Ostensorium
- Otey, James Hervey
- Outline of the Faith, An
- Oxford Movement, The
- Oxford Movement, The
- Oxford Movement, The
- Oxford Movement, The
- Oxon
