| 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 | Arthur Stanley Tritton |
| Arthur Surridge Hunt | Arthur Tansley | Arthur Township, Michigan |
| Arthur Waskow | Arthur Wellesley, 1st Duke of Wellington | Arthur Whitten Brown |
| Arthur William Hill | Arthur Wynne | Arthur, Illinois |
| Arthur, Iowa | Arthur, Nebraska | Arthur, North Dakota |
| Arthur, Wisconsin | Arthus reaction | Artibeus jamaicensis |
| Article (publishing) | Article 301 (Turkish Penal Code) | Article 9 of the Japanese Constitution |
| Articular capsule | Articular capsule of the knee joint | Articular disk |
| Articulated robot | Artificial bone | Artificial brain |
| Artificial cardiac pacemaker | Artificial consciousness | Artificial demand |
| Artificial flower | Artificial gene synthesis | Artificial heart |
| Artificial induction of immunity | Artificial insemination | Artificial intelligence |
| Artificial island | Artificial kidney | Artificial language |
| Artificial life | Artificial limb | Artificial lung |
