There are multiple definitions:

1. Uniform Resource Locator(English)

   • reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it
   • RDF, DLG
   • Data exchange
   • https://en.wiki…ia.org/wiki/URL

2. upper reference limit(English)

   • upper limit of the normal distribution
   • LRL, ULN, WNL, WRR
   • Statistics, Guidelines, Biomarker, Clinical chemistry
   • https://doi.org…linchem/hvaa158