| alternating current | corriente alterna |
| Alternating series | Serie alternada |
| Alternating series test | Prueba de las series alternas |
| alternation | rotación |
| alternative | alternativo |
| Alternative culture | Rock alternativo |
| Alternative Democratic Pole | Polo Democrático Independiente |
| Alternative history | Ucronía |
| Alternative libertaire | Alternative Libertaire |
| Alternative manga | Manga alternativo |
| alternative material | material alternativo |
| Alternative medicine | Medicina alternativa |
| Alternative metal | Alternative metal |
| Alternative propulsion | Propulsión alternativa |
| Alternative splicing | Ayuste alternativo |
| alternative technology | tecnologías alternativas |
| alternatively | en cambio |
| alternator | alternador |
| Alterswil | Alterswil |
| Altes Museum | Altes Museum |
| Althaea officinalis | Althaea officinalis |
| Althen-des-Paluds | Althen-des-Paluds |
| Althing | Alþingi |
| altho | aunque |
| althorn | trombón alto |
| although | aunque |
| Altiani | Altiani |
| Altichiero | Altichiero |
| Altiero Spinelli | Altiero Spinelli |
| Altillac | Altillac |
| altimeter | altímetro |
| Altingiaceae | Altingiaceae |
| Altino Arantes Building | Edificio del Banespa |
| Altiphrynoides | Altiphrynoides |
| Altiplano | Altiplano andino |
| Altirhinus | Altirhinus |
| Altispinax | Altispinax |
| altitude | elevación |
| altitude sickness | puna |
| Altkirch | Distrito de Altkirch |
| Altmark | Altmark |
| Altmarkkreis Salzwedel | Altmarkkreis Salzwedel |
| alto | contralto |
| Alto clarinet | Clarinete alto |
| Alto de El Angliru | Angliru |
| Alto Malcantone | Alto Malcantone |
| Alto Paraguay Department | Alto Paraguay |
| Alto Paraná Department | Departamento Alto Paraná |
| alto saxophone | saxofón alto |
| Alto Trás-os-Montes | Alto Trás-os-Montes |
| altocumulus | altocúmulo |
| Altocumulus Castellanu | Altocumulus castellanus |
| Altocumulus castellanus cloud | Altocumulus castellanus |
| Altocumulus cloud | Altocúmulus |
| Altocumulus undulatus cloud | Altocumulus undulatus |
| altogether | completamente |
| Altoparlante | Altavoz |
| Altorf | Altorf |
| Altos Hornos Zapla | Club Altos Hornos Zapla |
| altostratus | altostrato |
| Altostratus cloud | Altostratus |
| Altostratus undulatus cloud | Altostratus undulatus |
| Altrei | Anterivo |
| Altria Group | Altria Group |
| Altrice | Altricial |
| altrose | altrosa |
| altruism | altruismo |
| altruist | altruista |
| altruistic | altruista |
| Altstadt | Ciudad Vieja de Jerusalén |
| Altstätten | Altstätten |
| Altun Ha | Altún Ha |
| Altwiller | Altwiller |
| Altyn-Tagh | Falla de Altyn Tagh |
| Altzaga | Alzaga |
| Altötting | Distrito de Altötting |
| ALU | Unidad aritmético lógica |
| Alu Alkhanov | Alu Alkhanov |
| Alu sequence | Secuencia Alu |
| Alucard | Alucard |
| alum | alumbre |
| alumina | alúmina |
| aluminium | aluminio |
| aluminium container | envase de aluminio |
| aluminium content | contenido de aluminio |
| aluminium foil | papel aluminio |
| Aluminium gallium arsenide | Arseniuro de galio-aluminio |
| aluminium industry | industria del aluminio |
| Aluminium oxide | Alúmina |
| aluminosilicate | aluminosilicato |
| Aluminothermic reaction | Isoptera |
| aluminum | aluminio |
| Aluminum coating | Aluminizado |
| aluminum foil | papel de aluminio |
