It really depends on your OPS Manual.
Actually it depends upon your regulating authority.
IFR nav - approved navaids.
RNAV - approved enroute (above the MSA) navigation.
B-RNAV (RNP 5)- approved navigation below the MSA, when approved navaids are also available and monitored.
P-RNAV (RNP 1)- stand alone navigation below the MSA (terminal navigation, SIDs & STARS)
P-RNAV (RNP 0.5) - stand alone instrument approaches.