There are multiple definitions:

1. adaptive autoregressive(English)

   • TVAR

2. area at risk(English)

   • IS, UA, CMR, GRACE, IMH, IPC, MVO, MSI, RIC, TIMI, TTC
   • Cardiology
   • https://doi.org…acc.2019.05.024

3. antigen-antibody reaction(English)

4. active avoidance reaction(English)

5. acute articular rheumatism(English)

   • Rheumatology

6. activity-activity relationship(English)

   • between types of DNA modifications and tumor incidence reveals linear positive relationships between the log TD50 estimates and s-values for a series of mostly monofunctional alkylating agents
   • CBI, DD, DNA, HPRT, SAR
   • Biochemistry, Genetics
   • https://doi.org…5107(96)00032-2

7. aortic arch repair(English)

   • poses a major challlenge for surgeons and radiologists due to its tortuous anatomy and relevant side branches
   • CTA, EVAR, EVG, TEVAR
   • Anatomy, Vascular disease, Surgery, Medical imaging
   • https://doi.org…ME.2010.2053539

8. all arthroscopic repairs(English)

   • RC, DR, SR
   • Shoulder and other joints, Sports medicine
   • https://doi.org…363546516652900