- AMOC
- AMOLED
- AMP deaminase
- AMP-activated protein kinase
- AMPA
- AMPA receptors
- AMPS
- AMQP
- AMR
- AMS
- AMT
- AMiner
- AND gates
- AND-OR-Invert
- AND-inverter graph
- ANF
- ANFIS
- ANFO
- ANP
- ANSYS HFSS
- AOA
- AOD
- AOG
- AOI
- AP site
- AP-1 transcription factor
- AP1000
- AP600
- APAF1
- APC
- APCI
- API
- API gravity
- APL
- APQP
- APR-1400
- APU
- AQI
- AQM
- AR
- ARCore
- ARDS
- ARFF
- ARM
- ARP
- ARP cache
- ARPA
- ARPACK
- ART
- ARX
- AWS Lambda
- AWT
- Aarogya Setu
- Ab initio methods
- Abacus
- Abandoned mines
- Abandoned wells
- Abaqus
- Abbe refractometer
- Abbe sine condition
- Abbreviated Injury Scale
- Abdomen
- Abdominal aortic
- Abdominal cavity
- Abdominal muscles
- Abdominal obesity
- Abdominal trauma
- Abdominal wall
- Abductive reasoning
- Abelian group
- Abelian lie group
- Aberration
- Abietane
- Abietic acid
- Abinit
- Abiotic
- Abitibi Greenstone Belt
- Ablation
- Ablation zone
- Abnormal grain growth
- Above sea level
- Abrasion
- Abrasive flow machining
- Abrasive jet machining
- Abrasive machining
- Abrasive saws
- Abrasives
- Abrin
- Abscess
- Abscisic acid
- Abscissa
- Abscopal effect
- Absolute
- Absolute angular momentum
- Absolute configuration
- Absolute convergence
- Absolute geometry
- Absolute risk
- Absolute rotation
- Absolute scale