- A Kempis, Thomas
- A solis ortus cardine
- A.A.
- A.B.
- a.b.c., an
- A.C.
- A.D.
- A.J.
- A.M.
- A.M.D.G.
- A.P.A.
- A.R.M.
- A.S.C.
- A.S.C.J.
- A.S.S.P.
- Aachen, Germany, city of
- Aachen, Germany, diocese of
- Aaron
- Aaron of Caerleon, Saint
- Aaron, rod of
- Aaronites
- Ab Apostolici
- Ab.
- Abachum, Saint
- abacus
- abaddon
- Abaght, Saint
- Abagtha
- abandonment
- abba
- Abba Salama
- Abban
- abbé
- Abbe de Saint-Cyran
- abbess
- abbey
- abbey nullius
- abbey nullius of Belmont, North Carolina
- abbey nullius of New Norcia
- abbey nullius of Saint Peter
- abbey of Abingdon
- abbey of Ampleforth
- abbey of Athelney
- abbey of Bursfeld
- abbey of Bury Saint Edmunds
- abbey of Citeaux
- abbey of Clonmacnoise
- abbey of Corbey
- abbey of Corbie
- abbey of Crowland
- abbey of Croyland
- abbey of Dorchester, England
- abbey of Dryburgh, Scotland
- abbey of Echternach
- abbey of Einsiedeln
- abbey of Epternach
- abbey of Fleury
- abbey of Fontenelle
- abbey of Fontevrault
- abbey of Grottaferrata
- abbey of Mellifont
- abbey of Melrose
- abbey of Notre Dame du Lac
- abbey of Our Lady of Gethsemani
- abbey of Saint Albans
- abbey of Saint Emmeram
- abbey of Saint Gall
- abbey of Saint Michael and All Angels
- abbey of Saint Victor
- abbey of Saint Wandrille
- abbey of Sainte-Genevieve
- Abbey of Saints Vincent and Anastasius
- abbey of Sweetheart
- Abbey, Bath
- Abbey, Belmont
- Abbey, Benedictbeurn
- Abbey, Boyle
- Abbey, Buckfast
- Abbey, Cerne
- Abbey, Downside
- Abbey, Dunfermline
- Abbey, Evesham
- Abbey, Farnborough
- Abbey, Faversham
- Abbey, Folkestone
- Abbey, Fort Augustus
- Abbey, Fountains
- Abbey, Furness
- Abbey, Glastonbury
- Abbey, Hagustald
- Abbey, Hexham
- Abbey, Hextold
- Abbey, Holy Cross, Colorado
- Abbey, Holy Cross, Ireland
- Abbey, Holyrood
- Abbey, Jedburgh
- Abbey, Kilwinning
- Abbey, Kinloss
- Abbey, La Trappe
- Abbey, Maryhelp
- Abbey, Mount Melleray
- Abbey, Mount Saint Joseph
- Abbey, New
- Abbey, New Melleray
- Abbey, New Subiaco
- Abbey, Newbattle
- Abbey, Newhouse
- Abbey, Peterborough
- Abbey, Quarr
- Abbey, Ramsey
- Abbey, Ramsgate
- Abbey, Reading
- Abbey, Rievaulx
- Abbey, Rufford
- Abbey, Saint Anselm's
- Abbey, Saint Augustine
- Abbey, Saint Bede
- Abbey, Saint Benedict's, Kansas
- Abbey, Saint Benedict's, Oregon
- Abbey, Saint Benedict's, Scotland
- Abbey, Saint-Denis
- Abbey, Saint John's
- Abbey, Saint Martin's
- Abbey, Saint Mary's
- Abbey, Saint Maurice of Agaunum
- Abbey, Saint Meinrad's
- Abbey, Saint Michael's
- Abbey, Saint Norbert's
- Abbey, Saint Procopius'
- Abbey, Sherborne
- Abbey, Solesmes
- Abbey, Stanbrook
- abbeylubber
- Abbo of Fleury, Saint
- abbot
- abbot general
- abbot president
- abbot of unreason
- abbot primate
- abbot, commendatory
- abbot, lay
- abbot, regular
- abbot, secular
- abbot, titular
- Abbot, The
- abbreviations
- abbreviators, ecclesiastical
- Abdas, Saint
- Abdenago
- Abdias, bishop
- Abdias, book of
- abdication
- Abdon
- abduction
- Abecedarians
- Abel
- Abelard, Peter
- Abelians
- Abelites
- Abelli, Louis
- Abelonians
- Abercius, Inscription of
- Abercorn
- Abercromby, Robert
- Aberdeen Breviary
- Aberdeen, Scotland, diocese of
- Aberdeen, University of
- Abernethy, Perthshire, Scotland
- Abilene
- Abingdon, Abbey of
- Abiron
- abjuration
- ablution
- Abner
- Abomination of Desolation
- abortion
- abp.
- Abraham
- Abraham Anquetil-Duperron
- Abraham de Georgiis and Companions
- Abraham in Liturgy
- Abraham men
- Abraham Ortelius
- Abraham's Bosom
- Abraham's Oak
- Abram-men
- Abram Ryan
- Abrincalae
- abrogation
- Absalom
- absidiale
- absolute
- absolution
- Absolution, General
- Abstinence, Law of
- abthain
- abthane
- Abulfaraj
- Abundius, Saint
- Abundius, Abundantius, Marcianus, and John, Saints
- abuse of office
- abuse of power
- abyss
- Abyssinia
- Abyssinian Church
- Académie David
- Academies, Roman
- Acadia
- Acathistus
- Acca, Saint
- access
- acclamation
- accolade
- accommodation, Biblical
- Achaia
- Achaicus
- Achatius, Saint
- Achilleus, Saint
- Achilli, Giovanni Giacinto
- Achimelech
- achiropoeta
- Achitophel
- Achonry, Ireland, diocese of
- Acidalius, Valens
- acolouthia
- acolyte
- Acquaviva, Rudolph, Blessed
- Acre
- acrostic
- act of faith
- act of God
- Act of Settlement (English)
- Act of Settlement (Irish)
- Act of Supremacy
- Act of Toleration
- Act, Ecclesiastical Titles
- Acta Apostolicre Sedis
- Acta Sanctorum
- Acta Sanctorum Hiberniae
- Acta Sanctre Sedis
- Acta Triadis Thaumaturgae
- Action Francaise
- Acton, John
- Actor Ecclesire
- Acts and Monuments
- Acts of the Apostles
- Acts of the Martyrs
- Acts, Canonical
- Acts, Human
- Acts, Indifferent
- actual grace
- actual sin
- acus
- ad bestias
- ad libitum
- ad limina apostolorum
- ad metalla
- Ad Majorem Dei Gloriam
- Ad regias Agni dapes
- Adalard, Saint
- Adalbert, Saint
- Adam
- Adam de Marisco
- Adam de Marsh
- Adam's apple
- Adam's Peak
- Adam, fall of
- Adamnan, Saint
- Adauctus, Saint
- Addai, Saint
- Added, Saint
- Addeus, Saint
- Addeus and Maris, Liturgy of
- Adelaide Procter
- Adelaide, Australia, archdiocese of
- Adelphians
- Adeodatus I, Saint, Pope
- Adeodatus II, Saint, Pope
- Adeste Fideles
- adjuration
- administration Apostolic
- administration of the Sacraments
- administrator
- Admirabilis, Mater
- admonitions, canonical
- Ado, Saint
- Adolph Kolping
- Adonai
- adoption, canonical
- adoption, supernatural
- Adoptionism
- adoration
- Adoration of the Blessed Sacrament
- Adoration of the Cross
- Adoration of the Magi
- Adoration, Forty Hours'
- adoration, nocturnal
- adoration, perpetual
- Adoro Te devote, latens Deitas
- Adrian I, Pope
- Adrian II, Pope
- Adrian III, Pope
- Adrian IV, Pope
- Adrian V, Pope
- Adrian VI, Pope
- Adrian Dedel
- Adrian Fortescue, Blessed
- Adrian Turnebus
- Adrian of Canterbury, Saint
- Adrumetum
- Adullam
- adult
- adult Baptism
- adultery
- Advent
- Adventists
- Advertisements, Book of
- Advocate
- Advocate of God
- Advocate, Devil's
- Advocates of Roman Congregations
- advowson
- Aebbercurnig
- aecumenical councils
- Aedan of Ferns, Saint
- Aedh of Kildare, Saint
- Aedhan, Saint
- Ægidius a Columna
- Ægidius of Assisi, Blessed
- Ægidius Romanus
- Ægidius, Saint
- Aelfric the Grammarian
- Ælia Flaccilla
- Aengus, Saint
- aeon
- aer
- aesthetics
- Aeterna caeli gloria
- Aeterna Christi munera
- Aeterne Rector siderum
- Aeterne rerum Conditor
- Aeterne Rex altissime
- Affair, Kikuyu
- affections
- affirmative precepts
- affinity
- Afghanistan
- African Church
- African Methodist Episcopal Church
- African Methodist Episcopal Zion Church
- African Missions of Lyons
- African Rite
- Africanus, Julius
- Agabus, Saint
- Agag
- agape
- agapetae
- Agapetus I, Saint Pope
- Agapetus II, Pope
- Agapitus, Saint
- Agar
- Agatha, Saint
- Agathangelus Nourry, Blessed
- Agathius, Saint
- Agatho Saint, Pope
- Age of Discretion
- age of reason
- Age of Reason
- age, canonical
- age, impediment of
- Aged Poor Society
- Ages, Middle
- Aggeus
- aggressor, unjust
- Agios O Theos
- Aglar
- Aglipay, Gregorio
- Agnellus, Saint abbot
- Agnellus, Saint martyr
- Agnellus of Pisa, Blessed
- Agnes of Assisi, Saint
- Agnes of Bohemia, Blessed
- Agnes of Montepulciano, Saint
- Agnes of Prague, Blessed
- Agnes of Rome, Saint
- Agnesi, Maria Gaetana
- agnetz
- agnoetre
- Agnosticism
- Agnus Dei
- Agolanti, Chiara
- Agony of Christ
- Agostino Ciasca
- Agra, archdiocese of
- agrapha
- Agreda, Maria de
- Agricola (Bauer), Georg
- Agricius, Saint
- Aherne, Cornelius
- Ahriman
- Aidan, Saint
- Aiguillon, Marie de Vignerot de Pontcourlay, Duchess of
- Aikenhead, Mary
- Ailbe, Saint
- Ailleboust, Barbe d'
- Ailleboust, Louis d', Sieub de Coulanges
- Aillon, Joseph de la Roche d'
- Aimerich, Mateo
- Air Machine Blessing
- aisle
- Aix-la-Chapelle
- Aix-Marseilles, University of
- Ajmir, diocese of
- Alabama
- alabaster
- Alacoque, Margaret Mary, Saint
- Alain de la Roche
- Alais, Peace of
- Alamo, The
- Alan of Tewkesbury
- Alan of Walsingham
- Alanus de Rupe
- Alaric
- Alascans
- Alaska
- alb
- Alban, Epscop
- Alban Butler
- Alban of Mainz, Saint
- Alban, Saint
- Albanel, Charles d'
- Albania
- Albany
- Albany, New York, diocese of
- Albendorf
- Albert
- Albert of Brandenburg
- Albert of Brandenburg-Ansbach
- Albert the Great, Saint
- Alberta University Catholic College
- Alberto di Morra
- Albertus Magnus College
- Albertus Magnus, Saint
- Albigenses
- Albini, Charles Dominique
- Albornoz, Gil Alvarez Carillo de
- Albrecht
- Albrecht Dürer
- Albrecht von Haller
- Albright, Jacob
- Alcala, University of
- Alcala de Henares
- Alcantara, Military Order of
- Alcantara, Peter of, Saint
- Alcantarines
- Alciati, Giovanni Paolo
- Alcimus Ecdicius, Saint
- Alcmund, Saint
- Alcuin, Saint
- Aldegundis, Saint
- Aldhelm, Saint
- Aldric, Saint
- Aldus Manutius
- Alemany, Joseph Sadoc
- Aleppines
- Aleria, Corsica, diocese of
- Aleric
- Ales diei nuntius
- Alessandra Lucrezia Romola
- Alessandro di Mariano Filipepi
- Alessandro di Troja
- Alessandro Ludovisi
- Alessandro Manzoni
|
- Alessandro Scarlatti
- Alessandro Volta
- Alexander I, Saint, Pope
- Alexander II, Pope
- Alexander III, Pope
- Alexander III, the Great
- Alexander IV, Pope
- Alexander V, Pope
- Alexander VI, Pope
- Alexander VII, Pope
- Alexander VIII, Pope
- Alexander Briant, Blessed
- Alexander Goss
- Alexander Macdonell
- Alexander Natalis
- Alexander Nechay
- Alexander Neckam
- Alexander Newski, Saint
- Alexander Noel
- Alexander Pope
- Alexander Sauli, Saint
- Alexander Severus
- Alexander of Hales
- Alexander of Jerusalem, Saint
- Alexander the Charcoal Burner, Saint
- Alexander, Saint
- Alexander, Saint
- Alexandra, Christina
- Alexandria, Catechetical School of
- Alexandria, Catherine of, Saint
- Alexandria, Clement of
- Alexandria, Cyril of, Saint
- Alexandria, Dionysius of
- Alexandria, Egypt, city of
- Alexandria, Egypt, diocese of (Armenian rite)
- Alexandria, Egypt, diocese of (Latin rite)
- Alexandria, Louisiana, diocese of
- Alexandria-Cornwall, Canada, diocese of
- Alexandria, Patriarchate of
- Alexandria, Peter of, Saint
- Alexandrine Rite
- Alexians
- Alexis Falconieri, Saint
- Alexius, Saint
- Alfie Lambe
- Alford, Michael
- Alfred the Great
- Alfred Loisy
- Alfred Mame
- Alfred Volkmann
- Algeria
- Algu´,José
- alien houses
- alien priories
- Alighieri, Dante
- alimentation
- aliturgical days
- Aliwal, South Africa, diocese of
- All Glory, Laud, and Honor
- All Hallows
- All Hallows College
- All Praise to Saint Patrick
- All Saints, Feast of
- All Souls Day
- All Ye Who Seek A Comfort Sure
- All Ye Who Would Christ Descry
- all-
- Allah
- Allahabad, diocese of
- Allard, Paul
- allegiance
- allegiance, civil
- allegorical sense
- allegory
- Alleluia
- Alleluiatic Psalms
- Allen, Frances
- Allentown, Pennsylvania, diocese of
- Allerstein, August
- Alliance, Holy
- Allies, Mary Helen
- Allies, Thomas William
- Allion, Joseph de la Roche d'
- allocution
- Allouez, Claude
- Alma
- Alma Mater
- Alma Redemptoris Mater
- Almedha, Saint
- Almeida, John
- almoner
- almonry
- alms
- alms-bag
- alms-box
- alms-chest
- alms-day
- alms-deeds
- alms-folk
- alms-house
- alms-plate
- alms-Saturday
- Almsgiver, John the Saint
- Alonso de Espinosa
- Aloysius Gentili
- Aloysius Gonzaga, Saint
- alpha and omega
- alphabet, Cyrillic
- Alphabetic Psalms
- Alphonsa Hawthorne
- Alphonse Ratisbonne
- Alphonsus Lambe
- Alphonsus Liguori, Saint
- Alphonsus Rodriguez, Saint
- Alphonsus Salmeron
- Alrinus, Saint
- Alsace-Lorraine
- altar
- altar bell
- altar boys
- altar bread
- altar candles
- altar candlesticks
- altar canopy
- altar cards
- altar carpets
- altar cavity
- altar cloths
- altar cover
- altar crucifix
- altar curtains
- altar frontal
- altar herse
- altar horns
- altar in Scripture
- altar lamp
- altar lanterns
- altar ledge
- altar linens
- altar of repose
- altar of repository
- altar of Our Lady
- altar piece
- altar protector
- altar rail
- altar screen
- altar side
- altar societies
- altar steps
- altar stole
- altar stone
- altar tomb
- altar vase
- altar vessels
- altar wine
- altar, bye
- altar, double
- altar, epistle side of
- altar, fixed
- altar, Gospel side of
- altar, Gregorian
- altar, high
- altar, Lady
- altar, main
- altar, portable
- altar, privileged
- altar, stripping of the
- altarage
- altars in the temple of Jerusalem
- altars of the tabernacle
- altars, consecration of
- alternation
- Altham, John
- Altieri, Emilio
- Alto ex Olympi vertice
- Alton, Illinois, diocese of
- Altoona, Pennsylvania, diocese of
- Altotting
- altruism
- Alumbrados
- alumnus
- Alva, Fernando Alvarez de Toledo, Duke of
- Alvarez de Paz
- Alzog, Johann Baptist
- ama
- Amadeans
- Amadeus VIII
- Amadeus of the Heart of Jesus, Mother Mary
- Amalarius of Metz
- Amalberga, Saint
- Amalberga, Saint
- Amalecites
- Amalia, Saint
- Amalia, Saint
- Amana Society
- Amand, Saint
- Amarillo, Texas, diocese of
- ambassador
- ambition
- ambitus altaris
- ambo
- Ambrose, Saint
- Ambrose Lisle March Phillipps De Lisle
- Ambrose O'Higgins
- Ambrose of Siena, Blessed
- Ambrose Saint John
- Ambrose Shea
- Ambrosian Basilica
- Ambrosian Chant
- Ambrosian Hymnography
- Ambrosian Library
- Ambrosian Rite
- Ambrosiani
- ambry
- ambulatory
- amen
- amende honorable
- America (land)
- America (publication)
- America, Catholic Daughters of
- America, Central
- America, Latin
- American and Foreign Christian Union
- American Board of Catholic Missions
- American Catholic Church
- American Catholic Historical Association
- American Catholic Quarterly Review
- American College, Louvain, Belgium
- American Federation of Catholic Societies
- American Martyrology
- American Party
- American Protective Association
- American Rescue Workers
- American Salvation Army
- American Samoa
- Americanism
- Amerigo Vespucci
- Amerikanisches Familienblatt
- Amerikanski Slovenec
- amice
- Amida, Turkey, archeparchy of
- Amiens, France
- Amiot, Jean Joseph Marie
- Ammen, Daniel
- Ammonian Sections
- Ammonites
- Amorrhites
- Amos
- amovability
- Ampere, Andre Marie
- amphitheater
- Amphitheater, Flavian
- amphorre
- Ampleforth, abbey of
- Ampthill, Odo Russell, Baron
- ampullae
- amra
- Amraphel
- Amsterdam
- amulet
- Anabaptists
- anabolagium
- Anacletus, Saint, Pope
- Anacletus I
- Anacletus II
- Anagni, Italy
- anagnostes
- anagogical sense
- analecta
- Analepsis
- analogy
- Anammelech
- Ananias
- anaphora
- anarchy
- Anastasia, Saint
- anastasimatarion
- Anastasis, Church of the
- Anastasius I, Saint, Pope
- Anastasius II, Pope
- Anastasius III, Pope
- Anastasius IV, Pope
- Anastasius Bibliothecarius
- Anastasius the Fuller, Saint
- Anastasius, Saint
- anathema
- Anatole de Bengy
- anatomy
- ancestor worship
- Anchieta, Jose de
- anchor
- anchor cross
- Anchorage, Alaska, archdiocese of
- anchoress
- anchorhold
- anchorite
- ancien regime
- Ancient of Days
- ancients
- ancilla Dei
- Ancilla Domini Sisters
- Ancren Riwle
- Andalusia, Spain
- Andéol, Saint
- Anderdon, William Henry
- Anderson, Henry James
- Anderson, Patrick
- Andorra
- Andrada, Antonio de
- Andras van Wesele
- Andre Dumont
- Andrea Cesalpino
- Andrea d'Agnolo
- Andrea del Sarto
- Andrea della Robbia
- Andrea Doria
- Andrea Palladio
- Andrea Pisano
- Andrea Santoro
- Andrea, Giovanni d'
- Andreas Hofer
- Andreas Pozzo
- Andreas Vesal
- Andreas Vesalius
- Andreis, Felix de
- Andres Quintana
- Andrew, Saint
- Andrew Avellino, Saint
- Andrew Bobola, Saint
- Andrew Corsini, Saint
- Andrew Dotti, Blessed
- Andrew Gordon
- Andrew of Crete, Saint
- Andrew of Rinn, Blessed
- Andrew of Wyntoun
- Andrew the Scot, Saint
- Andrews, William Eusebius
- Andronicus
- anesthesia
- angel
- angel lights
- Angel of Great Counsel
- angel, guardian
- Angel, Thy Holy
- Angel-Guardians of Men, Spirits and Powers We Sing
- Angela Merici, Saint
- Angela of Foligno, Blessed
- Angeli, Girolamo degli
- Angelic Hymn
- Angelic Salutation
- Angelici
- Angelico, Fra
- Angélique Bullion
- Angelo Carletti di Chivasso, Blessed
- Angelo Corrario
- Angelo Correr
- Angelo Mai
- Angelo Secchi
- angels in art
- Angels of the Churches
- Angelus
- angelus bell
- Angelus de Scarpetti, Blessed
- Angelus, The
- anger
- Angers, France, diocese of
- Angers, University of, France
- Anglesey, Henry Paget, 1st Marquess of
- Anglican
- Anglican Church, disestablishment of the
- Anglican Councils
- Anglican Orders
- Anglin, Timothy Warren
- Anglo-Catholics
- Anglo-Saxon Church
- Angola
- Anguilla
- angustia loci
- Aniane, Benedict of, Saint
- Anicetus, Saint, Pope
- Anima Christi, sanctifica me
- animals, worship of
- animals in Christian art
- animism
- anise
- Anna
- Anna Maria Taigi, Blessed
- annals
- Annals of the Four Masters
- Annas
- annates
- Anne, Saint
- Anne Catherine Emmerich
- Anne Hanson Dorsey
- Anne Madeleine Remuzat, Venerable
- Anne of Denmark
- Annetta Bentivoglio
- annex chapel
- annihilation
- Annihilationism
- anniversary
- Annotinum Pascha
- Annuaire pontifical catholique
- annulment
- Annum Ingressi
- Annunciation of the Blessed Virgin Mary
- Annunziata, Order of the
- anoint
- Anquetil-Duperron, Abraham Hyacinthe
- ansata, crux
- Anschar, Saint
- Ansegisus, Saint
- Anselm, Saint
- Anselm of Lucca, Saint
- Anselmo Baggio
- Anstey, Thomas Chisholm
- ant.
- antecedent grace
- antediluvians
- antependium
- Anterus, Saint, Pope
- Anthony, Saint
- Anthony, Sister
- Anthony Baldinucci, Blessed
- Anthony Daniel, Blessed
- Anthony Kohlmann
- Anthony Maas
- Anthony Zaccaria, Saint
- Anthony of Padua, Saint
- Anthony van Dyck
- Anthony's Fire, Saint
- Anthoon van Dyck
- anthropology
- anthropomorphism
- anti-
- Anti-Mission Baptists
- anti-paedobaptists
- anti-pope
- anti-Semitism
- Antibes Legion
- antichrist
- anticipate
- Antidicomarianites
- antidoron
- Antigonish, Canada, diocese of
- Antigua
- Antimasonic Party
- Antimasons
- antimensium
- Antinomianism
- Antinomies
- Antinomy
- Antioch, Ignatius of, Saint
- Antioch, Maximilian of, Saint
- Antioch, Pisidia
- Antioch, School of
- Antioch, Syria
- Antiochene Rite
- Antipas, Herod
- Antipas, Saint
- Antipasch
- antiphon
- antiphon, communion
- antiphon, final
- antiphonary
- Antiphons, Great
- Antiphons, O
- antipodes
- antipope
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- Antitrinitarians
- antitype
- Antoine d'Abbadie
- Antoine de la Mothe Cadillac
- Antoine Gaubil
- Antoine Magaud
- Antoine Maillard
- Antoine Ozanam
- Antoinette, Marie
- Antonelli, Giacomo
- Antonio Allegri Correggio
- Antonio Canova
- Antonio da Sangallo, the Elder
- Antonio da Sangallo, the Younger
- Antonio de Sedella
- Antonio Escobar y Mendoza
- Antonio Espejo
- Antonio Margli, Venerable
- Antonio Rosmini-Serbati
- Antonians
- Antoninus, Saint
- Antoninus of Pamiers, Saint
- Antra deserti, teneris sub annis
- Antwerp
- Antwerp Bible
- Anvers
- anvil
- Ap. Sed. Leg.
- ape-men
- Apelles, Saint
- Apiarius of Sicca
- Apocalypse
- Apocalypse, Four Horsemen of the
- Apocalypse, Four Horses of the
- apocalyptic candlestick
- apocalyptic number
- apocatastasis
- Apocreos
- apocrisiarius
- apocrisiary
- apocrypha
- Apodeipnon
- Apodosis
- Apollinarianism
- Apollinaris, Saint
- Apollinaris Claudius, Saint
- Apollo
- Apollonia, Saint
- Apollyon
- apologetics
- apologia
- apologist, Christian
- Apolusia
- Apolysis
- Apolytikion
- Apophthegmata Patrum
- apostasy
- Apostate, Julian the
- Apostle in Liturgy
- Apostle spoons
- Apostle, Philip the
- Apostles
- Apostles of Erin, The Twelve
- Apostles other than the Twelve
- Apostles' Creed
- Apostleship of Prayer
- Apostleship of the Sea
- Apostolate, Liturgical
- Apostolic Blessing
- Apostolic Camera
- Apostolic Canons
- Apostolic Chancery
- Apostolic Church Ordinance
- Apostolic churches
- Apostolic Clerics of Saint Jerome
- Apostolic Constitutions
- Apostolic Dataria
- Apostolic delegate
- apostolic examiners
- apostolic expeditors
- Apostolic Indulgences
- Apostolic King
- Apostolic Letters
- Apostolic Mission House
- Apostolic Nunciature
- Apostolic schools
- Apostolic See
- Apostolic Signatura
- Apostolic Succession
- Apostolic Union of Secular Priests
- apostolic visitor
- Apostolic, administration
- Apostolic, College
- apostolic, preacher
- Apostolic, Prefect
- Apostolic, Prothonotary
- Apostolicae Sedis Gratia
- Apostolicity
- apotheosis
- apparition of Our Saviour
- apparition of the Infant Jesus
- apparitions
- apparitor
- appeal
- Appellant Controversy
- appetite
- Appian Way
- apple
- apple of Cain
- apple of Sodom
- apple, Adam's
- apple, Dead Sea
- approbation
- appropriation
- Apries
- Apronianus, Cemetery of
- apse
- apse chapel
- apsidiole
- aquamanile
- Aquarians
- Aquila and Priscilla
- Aquileia
- Aquileian Rite
- Aquitaine, Prosper of, Saint
- Arabia
- Aragon
- Aragon, Catherine of
- Aramaic
- Aran, Monastic school of
- Arbroath
- Arbuthnott Missal
- Arbutus unedo
- arca
- Arcadelt, Jacob
- Arcadius, Saint
- arch
- arch-
- Arch-Abbey, Saint Vincent's
- archabbot
- Archaeology, Christian
- Archaeology, Commission of Sacred
- archangel
- Archangel, Gabriel the
- Archangel, Michael the
- archbishop
- Archchancellor of the Empire
- archchaplain
- archconfraternity
- Archconfraternity of Christian Mothers
- Archconfraternity of the Holy Face
- archdeacon
- archdiocese
- archdioceses, list of
- Arches, Court of
- archid.
- Archiep.
- archiepiscopal cross
- archiereus
- archimandrite
- archiparaphonista
- Archippus, Saint
- archiprb.
- architecture, Byzantine
- architecture, ecclesiastical
- architecture, Gothic
- architecture, Latin
- architecture, Lombardic
- architecture, Norman
- architecture, Renaissance
- architrave
- Archives of the Holy See
- archives, diocesan
- Archives, Vatican
- archpresbytery
- archpriest
- Archpriest Controversy
- arcosolium
- Arcturus
- arculre
- Ardagh, Ireland, diocese of
- Ardagh Chalice
- Ardchattan, prioy of
- Ardente, Chambre
- ardente, chapelle
- area
- Areopagite
- Areopagite, Dionysius the, Saint
- Areopagitica
- Areopagus
- Arethas and Companions, Saint
- Argenson, Pierre de Voyer, Viscount d'
- Argenteuil, France
- Argentina
- argia
- arguing
- argument
- Argyll and the Isles, Scotland, diocese of
- Arianism
- Ariel
- Arimathea
- Arimathea, Joseph of, Saint
- Aristarchus of Thessalonica, Saint
- Aristides
- Aristotle
- Arius
- Arizona
- ark
- Ark and Dove
- Ark of the Covenant item
- Ark of the Covenant person
- Arkansas
- Arles, Caesarius of, Saint
- Arles, Genesius of, Saint
- Arlington, Virginia, diocese of
- Arma Christi
- Armada, The Spanish
- Armagedon
- Armagh, Ireland, archdiocese of
- Armagh, Book of
- Armagh, School of
- Armand Fizeau
- Armenia
- Armenian College
- Armenian Rite
- Armidale, Australia, diocese of
- Arminianism
- armor
- army bishop
- Arnold of Brescia
- Arnoudt, Peter Joseph
- Arnulf of Metz, Saint
- Arphaxad
- Arras, Boulogne and Saint-Omer, France, diocese of
- arrow
- art, Byzantine
- art, Christian
- art, Passion of Christ in
- Artemius Megalomartyr, Saint
- Arthur Jones
- Arthur Marshall
- Arthur Moore
- Arthur, King
- Articles, Fundamental
- Articles, Gallican
- Articles, Lambeth
- articles, organic
- Articles, Six
- articulo mortis
- Artoklasia
- Arts, Master of
- Arundel and Brighton, England, diocese of
- Arundell, Henry
- Arundell, Humphry
- Arundell, Thomas 1560
- Arundell, Thomas 1584
- As Fades the Glowing of Day
- Asaph, Saint
- ascendancy
- Ascension
- Ascent of the Scorpion
- asceteby
- asceterion
- ascetical theology
- asceticism
- aseity
- Aser
- ash color, vestments of
- Ash Wednesday
- Asher
- ashes, blessed
- Ashford University
- Ashmedai
- Ashtoret
- Asia Minor
- Asia, Proconsular
- Asicus, Saint
- Asmodeus
- asp
- asperges
- aspergill
- aspirations
- ass
- Ass in Caricature of Christian Beliefs and Practices
- ass worship
- Assam, British India, Prefecture Apostolic of
- Assemblies of God
- Assemblies of the French Clergy
- assembly, freedom of
- Asses, Feast of
- Assic, Saint
- Assideans
- Assisi, Agnes of, Saint
- Assisi, Clare of, Saint
- Assisi, Francis of, Saint
- assistance of the Holy Ghost
- Assistant at the Pontifical Throne
- assistant priest
- Association Catholique de la Jeunesse Francaise
- Association for the Protection of Belgian and Dutch Immigrants
- Association for Venerating the Martyrs in the Catacombs
- Association of Pentecostal Churches of America
- Association of the Holy Childhood
- Association, Catholic
- Association, Catholic Educational
- Association, Leopoldine
- Associations Cultuelles
- Associations Law
- Assuerus
- Assumption Abbey
- Assumption College
- Assumption of the Blessed Virgin Mary
- Assumption, Little Sisters of the
- Assumptionists
- Assyria
- Assyrian Captivity
- Assyrian Rite
- Astaroth
- Astarte
- Astericus Anastasius, Saint
- asterisk
- Astley Paston Cooper
- Astrik-Anastaz, Saint
- astrology
- astronomer
- astronomy
- Asturias
- asylum
- asylums, foundling
- At The Cross Her Station Keeping
- At The Lamb's High Feast We Sing
- At This Our Solemn Feast
- Ateneo of Manila
- Athalie
- Athanasian Creed
- Athanasius Kircher
- Athanasius, Saint 2 May
- Athanasius, Saint 15 Jul
- atheism
- Athelney, Abbey of
- Athenagoras
- Athenry, Galway, Ireland
- Athens, Dionysius of, Saint
- Athleta Christi nobilis
- athlete, Christian
- Athos, Mount
- Atilanus, Saint
- Atlanta, Georgia, archdiocese of
- atrium
- atonement
- Atonement, Day of
- Attala, Saint
- attention
- Attila
- Attilanus, Saint
- Attiret, Jean Denis
- Attracta, Saint
- attributes, divine
- attrition
- Aubrey Thomas Hunt De Vere
- Auckland, New Zealand, diocese of
- Auctor beate saeculi
- Audi benigne Conditor
- Audiences, Papal
- audientes
- Audifax, Saint
- Audit tyrannus anxius
- auditor
- Audley, Edmund
- Audry, Saint
- aufklarung
- Augouard, Philippe Prosper
- Augsburg, Germany, diocese of
- Augsburg, Religious Peace of
- augurs
- August von Schlegel
- Augusta Drane
- Auguste Broglie
- Auguste de Lapparent
- Auguste Nelaton
- Augustin a Banta Maria
- Augustin Blanchet
- Augustin Cauchy
- Augustin de Backer
- Augustin Fresnel
- Augustin Quintano
- Augustine Calmet
- Augustine Hewit
- Augustine of Canterbury, Saint
- Augustine of Hippo, Saint
- Augustine Novellus, Blessed
- Augustine Schoeffler, Saint
- Augustine Webster, Saint
- Augustinian Canons
- Augustinians canons
- Augustinians hermits
- Augustinians of the Assumption
- Augustinism
- Augustinus Lehmkuhl
- Augustus Pugin
- Augustus, Caius Julius Caesar Octavianus
- Aulneau, Jean Pierre
- aumbry
- aureole
- aureole of the saints
- auricular confession
- Auriesville, New York
- Aurora caelum purapurat
- Aurora jam spargit polum
- Aurora soli praevia
- austerities
- Austin Canons
- Austin Friars
- Austin, Texas, diocese of
- Australasia
- Australia
- Australian Catholic Truth Society
- Austremonius, Saint
- Austria
- Austria, John of, Don
- authentic
- authenticity
- Author and Finisher of Faith
- Author of Life, The
- authority
- Authorized Version
- auto-da-fé
- autocephali
- autos sacramentales
- Autricum
- Autun, Inscription of
- Auxentius, Saint
- Auxerre, France
- Auxerre, Germain of, Saint
- auxiliary bishop
- Auxilium Christianorum
- Auzalie of Barcelona, Saint
- Avalon
- avarice
- Ave Maria term
- Ave Maria english publication
- Ave Maria slovenian publication
- Ave Maria Stella
- Ave Regina Caelorum
- Ave verum Corpus natum
- Avellana
- Avellino, Andrew, Saint
- Averroes
- aversion
- Avesta
- aviators
- Avignon
- Avila, John of, Blessed
- Avila, University of
- Avitus, Saint
- Aviz, Military Order of
- Avranches
- awl
- ax
- axinomancy
- Ayllon, Lucas Vasquez de
- Ayr, Scotland
- Ayscough, John
- Azarias, Brother
- Azevedo, Ignatius de, Blessed
- Azevedo, Luiz de
- azure vestments
- azymes
- Azymes, Feast of
- Azymites
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