There are multiple definitions:

1. differentiation inducing factor(English)

2. differential item functioning(English)

   • a statistical characteristic of an item that shows the extent to which the item might be measuring different abilities for members of separate subgroups
   • IRT, MH, EITC, PPQ, PPQ-8
   • Statistics, Questionnaire
   • https://en.wiki…tem_functioning
   • https://doi.org…55/2021/6528891

3. direct immunofluorescence(English)

   • BP, IgG
   • Fluorescence, Dermatology
   • https://doi.org…229-5178.146170

4. difficulty in identifying feelings(English)

   • IDS, RD
   • Psychology
   • https://doi.org…ych.2012.01.002