| Arno Dorian | Arno Holz | Arno Tausch |
| Arnold | Arnold Badjou | Arnold Bouka Moutou |
| Arnold Bruggink | Arnold Classic | Arnold J. Toynbee |
| Arnold Mühren | Arnold Mvuemba | Arnold O. Beckman |
| Arnold Palmer | Arnold Schwarzenegger | Arnold Sommerfeld |
| Arnold van Gennep | Arnold von Harff | Arnold Wetl |
| Arnold Wilson | Arnold, Nebraska | Arnold, Pennsylvania |
| Arnold–Chiari malformation | Arnoldo Alemán | Arnolds Park, Iowa |
| Arnoldsville, Georgia | Arnolfo di Cambio | Arnolol |
| Arnoud van Doorn | Arnsberg | Arnsberg (region) |
| Aroideae | Aroma Park, Illinois | Aromanian language |
| Aromat | Aromatase | Aromatherapy |
| Aromatic acid | Aromatic compound | Aromatic hydrocarbon |
| Aromaticity | Aron Baynes | Aron Kader |
| Aron Schmidhuber | Aron Winter | Aronia |
| Aroostook County, Maine | Aroser Rothorn | Aroser Weisshorn |
| Arouna Koné | Around the Moon | Around the Pink House |
| Around the World in 80 Days (1956 film) | Around the World in 80 Days (2004 film) | Around the World in Eighty Days |
| Arousal | Arp 116 | Arpanet |
| ARPANET | Arpelistock | Arpin (town), Wisconsin |
| Arpin, Wisconsin | Arquebus | Arques, Pas-de-Calais |
| Arrabia | Arracacia | Arracacia atropurpurea |
| Arracacia equatorialis | Arracacia ovata | Arracacia peruviana |
| Arracacia rigida | Arracacia xanthorrhiza | Arrai TV |
| Arranged marriage | Arrangement | Array data structure |
| Arraya 2 | Arrest and assassination of Ngo Dinh Diem | Arresting gear |
| Arrhenatherum | Arrhenatherum affine | Arrhenatherum album |
| Arrhenatherum angustifolium | Arrhenatherum calderae | Arrhenatherum elatius |
| Arrhenatherum ilievii | Arrhenatherum intermedium | Arrhenatherum kotschyi |
| Arrhenatherum longifolium | Arrhenatherum palaestinum | Arrhenatherum pallens |
| Arrhenatherum paulianum | Arrhenatherum phaenoneuron | Arrhenatherum pragense |
| Arrhenatherum rupestre | Arrhenatherum scabrinsculum | Arrhenatherum scabrum |
| Arrhenatherum submuticum | Arrhenatherum sylvaticum | Arrhenia lobata |
| Arrhenius equation | Arrhenius plot | Arrhythmia |
| Arrhythmogenic right ventricular dysplasia | Arrian | Arriba, Colorado |
| Arrietty | Arrigo Sacchi | Arrondissement |
| Arrondissements of France | Arrow | Arrow (Israeli missile) |
| Arrow (TV series) | Arrow 3 | Arrow Emblem: Hawk of the Grand Prix |
| Arrow of time | Arrow Point, Missouri | Arrow Rock, Missouri |
| Arrow Sport | Arrowsmith (film) | Arrowsmith, Illinois |
| Arroyomolinos | ARS | Arsanilic acid |
| Arsène Lupin | Arsène Wenger | Arsen Avetisyan |
| Arsenal F.C. | Arsenic | Arsenic acid |
| Arsenic contamination of groundwater | Arsenic pentachloride | Arsenic pentoxide |
| Arsenic tribromide | Arsenic trichloride | Arsenic triiodide |
| Arsenic trioxide | Arsenic triselenide | Arsenic trisulfide |
| Arsenic(III) chloride | Arsenic(V) oxide | Arsenide |
| Arsenopyrite | Arsenous acid | Arshad al-Umari |
| Arshad Warsi | Arshaq Sharqi Rural District | Arshaq-e Sharqi Rural District |
| Arsine | Arsole | Arson |
| Arsphenamine | ART | Art |
| ART america | Art Attack | Art Carney |
| Art Deco | ART Europe | ART europe |
| Art Gallery of Ontario | Art Infusion | Art Malik |
| Art Nouveau | Art Parkinson | ART Teenz |
| Art therapy | Art world | ART افلام |
| Art الليث | ART المفتوحة | ART الموسيقى |
| ART المنوعات | ART المناهج | ART المناسبات |
| ART الحكايات | ART الطرب | ART العالمية |
| ART سينما | Art سبورت | ART سبورت (الرياضية) |
| ART عين | Artamus | Artas, South Dakota |
| Artaxerxes I of Persia | Artémidore | ArtCyclopedia |
| Artem Mikoyan | Artem Milevskiy | Artemia |
| Artemidorus | Artemis | Artemisia |
| Artemisia absinthium | Artemisia annua | Artemisia atrata |
| Artemisia campestris | Artemisia dracunculus | Artemisia genipi |
| Artemisia Gentileschi | Artemisia glacialis | Artemisia herba-alba |
| Artemisia judaica | Artemisia lactiflora | Artemisia ludoviciana |
| Artemisia maritima | Artemisia pontica | Artemisia stelleriana |
| Artemisinin | Artemotil | Arterial arcades |
| Arterial blood | Arterial blood gas | Arterial catheter |
| Arterial hypertension | Arterial resistivity index | Arterial tree |
| Arteries | Arteriole | Arteriosclerosis |
| Arteriovenous fistula | Arteriovenous malformation | Arteriviridae |
| Arterivirus | Artery | Artery of bulb of penis |
| Artery of bulb of vestibule | Artery of round ligament of uterus | Artery to the ductus deferens |
| Artesia, Mississippi | Artesian aquifer | Artesian, South Dakota |
| Artesunate | Artesunate/amodiaquine | Arthralgia |
| Arthritis | Arthritis mutilans | Arthrodermataceae |
| Arthrodesis | Arthrogrryposis | Arthrogryposis |
| Arthrology | Arthropod | Arthropoda |
| Arthroscopy | Arthur (1981 film) | Arthur Aaron (footballer) |
| Arthur Andersen | Arthur Ashe | Arthur Balfour |
| Arthur Bernardes (football manager) | Arthur Bisguier | Arthur Boka |
| Arthur C. Clarke | Arthur C. Clarke Award | Arthur Casagrande |
| Arthur Cayley | Arthur Compton | Arthur Conan Doyle |
| Arthur Cox (footballer) | Arthur Cronquist | Arthur de Gobineau |
| Arthur Demarest | Arthur Dimmesdale | Arthur Eddington |
| Arthur Eichengrün | Arthur Evans | Arthur Golden |
| Arthur Harden | Arthur Hays Sulzberger | Arthur Henderson |
| Arthur Henry Reginald Buller | Arthur Holmes | Arthur Honegger |
| Arthur Huber-Morath | Arthur J. Arberry | Arthur Jaffe |
| Arthur Jeffery | Arthur john arberry | Arthur John Arberry |
| Arthur Johnson (manager) | Arthur Kingsley Porter | Arthur Koestler |
| Arthur Kornberg | Arthur Laffer | Arthur Leonard Schawlow |
| Arthur Miller | Arthur Numan | Arthur Ponsonby, 1st Baron Ponsonby of Shulbrede |
| Arthur Q. Bryan | Arthur Ravenel Jr. Bridge | Arthur Rimbaud |
| Arthur Rubinstein | Arthur Ruppin | Arthur Scherbius |
| Arthur Schmidt (film editor) | Arthur Schnitzler | Arthur Schopenhauer |
| Arthur Schuster | Arthur Seyss-Inquart | Arthur Stanley Eddington |
