olemus
Wiktionary:
8. a relation between objects in which one object designates, or acts as a means by which to connect to or link to, another object

ülevaateid
https://en.wikipedia.org/wiki/Reference

näiteid
reference axes -- baaskoordinaadistik
reference date -- aluskuupäev
reference diode-- tugidiood
reference frequency -- tugisagedus
reference node -- baassõlm
reference point -- tugipunkt
reference value -- tugiväärtus
reference voltage -- tugipinge