There are multiple definitions:

1. defined daily dosis(English)

   • assumed average maintenance dose per day for a drug used for its main indication in adults
   • ATC
   • Pharmacology / pharmaceutics
   • https://www.who…eral_considera/

2. dual-chamber cardiac pacing, dual sensing, triggered plus inhibited sensing(English)

   • DDDR
   • Cardiology

3. dermatitis, diarrhea, dementia(English)

   • DDDD
   • Dementia, Dermatology

4. degenerative disc disease(English)

   • a major cause of low back pain. In these cases TDR is a safe and effective treatment of lumbar discogenic low back pain
   • cDDD, LBP, TDR, DH, ALD, ALL, DSPL, LTJR, NRS, ODI, ROM, TLIF, ACDF, AE, CAC, CDA, FDA, FSU, HO, HPD, IDE, LP, MCS, NDI, PCS, SF-36
   • Spine (or spinal cord), Pain, Therapeutic approaches
   • https://doi.org…352/ijsr.000019
   • https://doi.org…3287-019-1440-5
   • https://doi.org…0586-006-0294-6
   • https://doi.org…6.10.SPINE16264
   • https://doi.org…neu.2018.01.157

5. difference-in-difference-in-difference(English)

   • a triple difference approach. Allows for changes of time trends in outcomes across different (e.g. SES) levels within the treatment group to be compared to their counterparts in the control group over time
   • ACA, CHAMPUS, DD, SES, SPARCS
   • Statistics
   • https://doi.org…37.2021.1974715

6. dense deposit disease(English)

   • see also C3 glomerulonephritis
   • CGN, EM, C3GP
   • Nephrology
   • https://doi.org…55/2021/6295543