| Ac | Acab | Acacia |
| Acacia glauca | Acacias, Meta | Acad |
| Academia Filipina de la Lengua Española | Academia filipina de la lengua española | Academic discipline |
| Academic field | Academic journal | Academy |
| Academy of Hebrew Wika | Acadiano | Acadio |
| Acala | Acandí | Acanthocephala |
| Acanthodii | Acapulco | Acarus |
| Acarus scabiei | Acasa TV | Acate |
| Acaz | Acılıqbinə | Accad |
| Accademia Nazionale di Santa Cecilia | Accadia | Accadian |
| Accadiano | Accadianong Imperyo | Acceglio |
| Accel World | Accelerate | Acceleration |
| Accelerator physics | Accentor | Acceptance sampling |
| Access Computer and Technical College | Accessories | Accessory |
| Accessory nerve | Accettura | Acchi Kocchi |
| Acciano | Acción y Reacción | Accident |
| Accidental abortion | Accidental bleeding | Accidental hemorrhage |
| Accidia | Accipiter gentilis | Accipiter nisus |
| Accipitridae | Acclimatisation | Acclimatise |
| Acclimatization | Acclimatize | Accommodate |
| Accommodating | Accommodation | Accomodation |
| Accompaniment | Accouchement | Accoucheur |
| Accoucheuse | Accountancy | Accountant |
| Accounting | Accounts payable | Accounts receivable |
| Accra | Accumoli | Accupuncture |
| Accusation | Ace Adrian Arellano Mendiola | Ace Espinosa |
| Ace Target Max | Ace Vergel | Acebo |
| Acebook | ACEBOOK | Acedia |
| Aceh | Aceh (lugar) | Aceite de oliva |
| Acerenza | Acerno | Acerra |
| Aceta | Acetabular | Acetabulum |
| Acetanilid | Acetanilide | Acetanilidum |
| Acetic | Acetic acid | Acetomorphine |
| Acetum | Acetylated morphine | Acetylcholine |
| Acevedo (Huila) | Acevedo, Huila | ACh |
| Achab | Achaemenid | Achaemenid dynasty |
| Achaemenid Empire | Achala | Achalasia |
| Achara | Acharra | Achí (Bolívar) |
| Achí, Bolívar | Ache | Acheng |
| Achery | Achery, Aisne | Achesa |
| Acheulean | Achi, Nagano | Achileo |
| Achille Ratti | Achillea millefolium | Achilleo |
| Achilles | Achilles heel | Achilles Samain |
| Achilles tendinitis | Achilles Tendinitis | Achilles tendinopathy |
| Achilles tendon | Achilles' heel | Achilles' tendon |
| Achilleus | Achillo | Achinsk |
| Achiote | Achmed sukarno | Achmed Sukarno |
| Acholeplasma | Acholeplasmataceae | Acholeplasmatales |
| Achuete | Achy Breaky Heart | Aci Bonaccorsi |
| Aci Castello | Aci Catena | Aci Sant'Antonio |
| Acid | Acid dyspepsia | Acid indigestion |
| Acid whey | Acidemia | Acidic |
| Acidimicrobium | Acidity | Acidobacteria |
| Acidosis | Acini | Acinonyx jubatus |
| Acireale | Acklins | Acnam, Nueva Era, Ilocos Norte |
| Acne | Acne rosacea | Acne vulgaris |
| Acoelomate | Acoelomorpha | Aconcagua |
| Aconcagua, Arhentina | Aconite | Aconite poison |
| Aconite poisoning | Aconite root | Aconite tincture |
| Aconitine | Acorn | Acosta's disease |
| Acosta, Batac | Acoustic | Acoustic engineer |
| Acoustic engineering | Acoustical engineering | Acoustics |
| ACQ-Kingdom Broadcasting Network | Acquacanina | Acquafondata |
| Acquaformosa | Acquafredda | Acquaint |
| Acquaintance | Acquainted | Acqualagna |
| Acquanegra sul Chiese | Acquapendente | Acquappesa |
| Acquarica del Capo | Acquaro | Acquasanta Terme |
| Acquasparta | Acquaviva Collecroce | Acquaviva d'Isernia |
| Acquaviva delle Fonti | Acquaviva Picena | Acquaviva Platani |
| Acquedolci | Acqui Terme | Acquired heart disease |
| Acquired immunodeficiency syndrome | Acre | Acre City |
| Acre, Israel | Acri | Acrilan |
| Acrisius | Acrobat | Acrobatics |
| Acrobats | Acromegaly | Acromia |
| Acromion | Acropolis | Acrylic |
| Acrylic fiber | Act of Apostle | Act of Apostles |
| Act of the Apostle | Act of the Apostles | Acta Apostolicae Sedis |
| Acte est fabula | Actin | Acting |
| Actinidia deliciosa | Actinium | Actinobacteria |
| Actinobacteridae | Actinomyces | Actinomycetaceae |
| Actinomycetales | Actinomycetes | Actinomycosis |
| Actinopterygii | Action genre | Action potential |
| ActionAid | ActionAid International (UK) | Active Design |
| Active Duty | Active window | Activision |
| Actor | Actress | ACTS Computer College |
| Acts of Apostles | Acts of the Apostle | Acts of the Apostles |
| Actual cautery | Actual politics | Actuarial Science |
| Actuator | Acupuncture | Acute |
| Acute disease | Acute illness | Acute sickness |
| Acuto | Acy | AD |
| AD 1 | Ad absurdum | Ad hominem |
| Ad infinitum | Ad interim | Ad lib |
| Ad Lib (estilo ng titik) | Ad Lib (tipo ng titik) | AD Police Files |
| Adab (city) | Adab (siyudad) | Adachi, Tokyo |
| Adad-nirari I | Adad-nirari II | Adalberto ng Praga |
| Adalberto ng Prague | Adam | Adam (paglilinaw) |
| Adam and Eve | Adam C. Powell, Jr. | Adam Cheng |
| Adam Clayton Powell | Adam Clayton Powell, Jr. | Adam Heydel |
| Adam Holm | Adam Lambert | Adam Lanza |
| Adam Levine | Adam Malik | Adam Petty |
