There are multiple definitions:

1. active pharmaceutical ingredient(English)

   • pharmacologically active part(s) of a formulation; in case of a salt, the active ingredient should be understood to include both, the therapeutic moiety and the appended portion of the molecule; the maximum acceptable deviation in the a.i. content of a finished product must not exceed ±5% at the time of manufacture
   • FDA, GAO, GMP, ACT, mRDT, CFD, DEM, DF, DPI, FPF
   • Pharmacology / pharmaceutics
   • https://link.sp…-211-89836-9_17
   • https://doi.org…arm.2021.120821

2. Association for Pathology Informatics(English)

   • Pathology, Medical informatics, Organizations (documentation)

3. application program interface(English)

   • ARM, DOM, DSP, IPC, Medline, OS, SAX, XML
   • Computing (biomedical), Machine learning
   • https://github.…oc#api-overview

4. Asian or Pacific Islanders(English)

   • SEER
   • Ethnicity, Epidemiology, Woman /female, Mammary gland, Oncology
   • https://doi.org…0549-005-9088-5

5. aortic pulsatility index(English)

   • a hemodynamic metric of cardiac function, calculated as (systolic−diastolic blood pressure)/pulmonary capillary wedge pressure (PCWP)
   • AMI, CO, CPO, DBP, EDP, EDV, Ees, HF, HR, MAP, PCWP, PE, PVA, RAP, SBP, SCAI, SV, PAPi, MPS, MVO2, PAC, SW
   • Hemodynamics, Emergency medicine, Cardiology, Ratio-based metric
   • https://doi.org…LURE.122.009601
   • https://doi.org…vm.2024.1365696

6. Alzheimer's Prevention Initiative(English)

   • refers to a composite cognitive test score
   • AD, CERAD, MMSE, MSDR
   • Alzheimer's disease, Preventive medicine, Cognitive function, Scoring systems/scales
   • https://doi.org…88/JCP.13m08927

7. Asociación Panamericana de Infectología(Spanish)

   • Pan-American Association of Infectious Diseases
   • COVID-19, SBI
   • Infection, Organizations (clinical)
   • https://www.apiinfectologia.org/

8. asthma predictive index(English)

   • mAPI
   • Asthma, Allergy, Pulmonology
   • https://doi.org…9/ped.2023.0016

9. average pixel intensity(English)

   • AML, BD, BMVP, CCT, CMRI, cVA, EROA, FED, LA, LVEF, LVSV, MA, MAD, MDCTA, ML, MR, MRF, MVP, PISA, PM, PML, SCD, STE, TEE, TI, TTE, VC, VCW
   • Medical imaging, Cardiology, Pathology
   • https://doi.org…shj.2022.100024