- A ... A-lo-pen
- A-mdo ... Aanteekening op de grondwet
- AAO ... Abancay
- Abandoned Museums ... Abbott Elementary
- Abbott, Anderson ... ʿAbd al-ʿAzīz ibn al-Ḥasan ibn Muḥammad al-Ḥasanī al-ʿAlawī
- ʿAbd al-ʿAzīz ibn Mitʿab ... Abdul-Qadir
- Abdülaziz ... Abercrombie, James
- Abercrombie, Lascelles ... Abijah, Lucy
- Abildgaard, Nicolai Abraham ... Abomunist Manifesto
- Abondio, Antonio ... Abrams, M.H.
- Abrams, Meyer Howard ... absolute motion
- absolute music ... Abū al-Hawl
- Abū al-Hayjāʾ ʿAbd Allāh ... Abū Muḥammad ʿAlī ibn Aḥmad ibn Saʿīd ibn Ḥazm
- Abū Mūsā ... Abu, Mount
- Abu-Jamal, Mumia ... acacia ant
- Acacia arabica ... acanthocytosis
- acanthodian ... accessio
- Accession, Treaty of ... accretor
- Accrington ... Acetobacterium woodii
- acetone ... Achilles
- Achilles ... Acipenser oxyrinchus
- Acipenser ruthenus ... acouchy
- acousmatics ... acrodonty
- acrodynia ... Actian Games
- Actias luna ... active force
- active galactic nucleus ... acute necrotizing ulcerative gingivitis
- acute otitis media ... Adak
- Adak Station ... Adams, Charles Francis, III
- Adams, Charles Francis, Jr. ... adaptive radiation
- adaptive resource management ... adduct
- adductor brevis muscle ... adenylate cyclase
- adenylic acid ... adipose cell
- adipose fin ... Administrative Behavior
- administrative budget ... Adonim
- Adonina ha-Levi ... Adrianople, Peace of
- Adrianople, Peace of ... Advent Christian Church
- Advent wreath ... advocacy network
- advocacy poll ... Aegypiinae
- Aegypius monachus ... aerial root
- aerial skiing ... Aesthetic as Science of Expression and General Linguistics
- aesthetic distance ... affective fallacy
- affective memory ... Afonso IV
- Afonso o Africano ... African goliath beetle
- African gray parrot ... African water rat
- African weaver ant ... After the Guns Fall Silent: The Enduring Legacy of Landmines
- After the Hunt ... Agallamh na Seanórach
- Agalliana ensigera ... Agazzi, Carolina
- Agazzi, Rosa ... ager publicus
- Ageratina altissima ... Aglaia
- Aglaia ... Agostino Di Duccio
- Agostino Di Giovanni ... Agriculture, U.S. Department of
- Agrigan ... Agul language
- Agulhas Current ... Ahl as-Sunnah
- Ahl-e Ḥaqq ... Ahn, Charles
- Ahn, Susan ... AIDS Memorial Quilt
- AIDS-related complex ... Ainslie, Ben
- Ainslie, Sir Charles Benedict ... air space
- air space ... airport
- Airport ... Ajar-Imeretinsky
- Ajaria ... Akaroa
- Akasaki Isamu ... Akhvlediani, Giorgi
- Akhyāliyyah, Laylā al- ... Akt und Sein
- Akt’ubinsk ... Ala Shan Desert
- Ala Wai Canal ... Alamūt
- Alamut ... Alaungpaya
- Alaungpaya Dynasty ... Albany, Henry Stewart, Duke of
- Albany, James, Duke of ... Albert the Bear
- Albert the Courageous ... Albizia lebbek
- Albizu Campos, Pedro ... Alcántara Bridge
- Alcántara, Order of ... alcohol abuse
- alcohol consumption ... Aldrich, Bess Genevra Streeter
- Aldrich, Lyman T. ... Alencar, José Martiniano de
- Alençon ... Alexander I, St.
- Alexander II ... Alexandria
- Alexandria ... Alfonso el Batallador
- Alfonso el Benigno ... algebraic linguistics
- algebraic map ... Ali Bash Hamba
- ʿAlī Bey ... Alien Resurrection
- alien species ... alkali lake
- alkali land ... All India Muslim League
- All India Radio ... All-England Championship
- All-England Championships ... Allegory of Love: A Study in Medieval Tradition, The
- Allegory of Prudence, An ... Allenby, Edmund Henry Hynman Allenby, 1st Viscount
- Allendale ... Alligator Creek, Battle of
- alligator fish ... Allstate Corporation
- Allston, Robert ... Almond, Edward Mallory
- Almond, Gabriel ... Alor Setar
- Alor Star ... Alpha Tauri
- Alpha Ursae Minoris ... Alpinia
- alpona ... Altdorfer, Albrecht
- alte Andreas, Der ... Altmark, Truce of
- Altmühl ... alunogen
- Alushta ... Am386 microprocessor
- AMA ... Amanita bisporigera
- Amanita brunnescens ... Amateur Skittle Association
- Amateur Softball Association of America ... Ambani, Mukesh
- Ambani, Mukesh Dhirubhai ... ambrette
- Ambridge ... amendments to the U.S. Constitution, list of
- Amendola, Giovanni ... American Art Association
- American Assassin ... American College Testing Exam
- American College: A Criticism, The ... American Gods
- American golden plover ... American League of Professional Baseball Clubs
- American Legion ... American President, The
- American Presidential Election ... American Standard Code for Information Interchange
- American Standard Version ... americium-241
- americium-242 ... Amida Triad
- amidah ... AMLO
- ʿAmm ... amodal perception
- Amodio, Matt ... Amours, Les
- Amoy ... amplifier, optical
- amplitude ... Amud
- Amud 1 ... An die Freude
- An I, L’ ... Anagallis
- Anagallis arvensis ... analytic proposition
- analytic psychology ... anarchist communism
- Anarchist Cookbook, The ... Anatolian rug
- Anatolian Turkish language ... Ancient Child, The
- Ancient Chinese language ... And Woman Was Created
- And Yet…... ... Anderson, Ken
- Anderson, Kenneth ... Andong
- Andoni-Ibeno ... Andrews University
- Andrews, Augustus George ... Andropogon hallii
- Andropogon saccharoides ... Ang-ch’ü
- aṅgā ... Angels & Demons
- Angels & Demons ... Angles
- Anglesey ... Ango, Jean
- Angol ... angwantibo
- Anhalt ... animal interlace
- Animal Kingdom ... Anjuman-i Fulad
- Anka, Paul ... Annals of the Turkish Empire from 1591–1659 of the Christian Era
- Annaly ... Annona × atemoya
- Annona cherimola ... anole
- Anolis ... anoxia
- Anoxypristis ... Answer As A Man
- answer engine ... antecedence
- antecedent ... Anthocharis
- anthocorid bug ... anthrozoology
- Anthurium ... anticancer drug
- Anticaria ... antihypertensive drug
- antiknock agent ... Antipater
- Antipater ... antiunionism
- Antivari ... Antrim Coast Road
- Antrim Mountains ... anxiolytic
- Anxious Bench, The ... Aouk
- Aoun, Joseph ... APDS
- Ape ... aphthous stomatitis
- Aphyocharax rubripinnis ... Apocynaceae
- Apocynum ... apologetics
- Apologeticum ... Apotgan
- apothecaries’ scruple ... Appendix on the Papacy
- Appendix Probi ... applied linguistics
- applied logic ... Apted, Michael
- Aptenodytes ... Aquanaut, The
- aquaplane ... Arab Executive
- Arab Feminist Union ... Arabis caucasica
- Arabiya News, Al ... aralia ivy
- Aralia nudicaulis ... Aravali Range
- Aravalli Range ... arc, electric
- Arc-en-Ciel ... archaism
- Archangel ... Architecte et l’empereur d’Assyrie, L’
- Architects Collaborative, The ... Arctic tern
- Arctic tundra ... Ardra
- Ards ... areola
- areole ... Argentine boa constrictor
- Argentine Confederation ... Argyll, Archibald Campbell, 10th Earl and 1st Duke of, Marquess Of Kintyre And Lorne, Earl Of Campbell And Cowall, Viscount Of Lochow And Glenyla, Lord Of Inverary, Mull, Morvern, And Tirie
- Argyll, Archibald Campbell, 10th Earl and 1st Duke of, Marquess of Kintyre and Lorne, Earl of Campbell and Cowall, Viscount of Lochow and Glenyla, Lord of Inverary, Mull, Morvern, and Tirie ... Arīḥā
- Arihant ... Aristoxenus
- Arita ... Arkwright, Sir Richard
- Arland, Marcel ... Armed Forces Day
- Armed Forces High Command ... armour
- armour ... Arnaut de Zwolle, Henri
- Arnavad Peak ... Arnulf von Kärnten
- Arnulfista Party ... Arran, James Hamilton, 1st earl of
- Arran, James Hamilton, 2nd earl of ... Arrow, Kenneth Joseph
- Arrow, Kenneth Joseph ... art
- art ... art theft
- art therapy ... Artemisia annua
- Artemisia dracunculus ... Arthurian legend
- Arthurian romance ... Artist, the
- Artist, The ... Arundale, Rukmini Devi
- Arundel ... as if, philosophy of
- As It Happened ... asbestiform habit
- asbestos ... ascorbic acid
- ascorbic acid oxidase ... Ashby-de-la-Zouch
- Ashcan School ... Ashokavadana
- ashoog ... Asian flu of 1957
- Asian flu pandemic of 1957 ... Askia Mūsā
- Askival ... aspergillic acid
- aspergilloma ... assassination of Martin Luther King, Jr.
- Assassination of Richard Nixon, The ... assisted suicide
- assistive robot ... Assyrian Genocide
- Assyrian incident ... Astor River
- Astor, Brooke Russell ... Astronomische Gesellschaft
- Astronomische Gesellschaft Katalog ... At Seventeen
- at sign ... Atawulf
- ataxia ... Athel tree
- Atheliales ... Athos, Mount
- Athrotaxis ... Atlantic languages
- Atlantic leatherback ... atmospheric absorption
- atmospheric arc lamp ... atomic size
- atomic slip ... Atrypa
- ATSB ... Atthidographer
- Atthis ... Au Bonheur des Dames
- Au Co ... Audion
- AudioNet ... Augsburg, Diet of
- Augsburg, League of ... auk family
- Auk Glacier ... Aurès
- aureus ... Austerlitz
- Austerlitz, Battle of ... Australian Colonies Government Act
- Australian Communications Authority ... Australophocaena dioptrica
- australopith ... auto
- Auto Acordado of 1713 ... automated teller machine
- Automated Transfer Vehicle ... autosome
- autostrada ... Avalonian orogeny
- Avalos, Ferdinando Francesco d’ ... Avenue of Flags
- Avenue of Mysteries ... Avignon Pietà
- Avignon school ... Awadh
- Awadhesh Pratap Singh University ... axial flow centrifugal pump
- axial locomotion ... Ayacucho, Battle of
- ayagapata ... Ayrer, Jakob
- Ayres Natural Bridge ... Azef, Yevno
- Azeglio, Massimo Taparelli, Marquess d’ ... AZS
- AZT ... aʿyān
