Evolutionary pathways for extragalactic radio sources. Mtype 2 double sources will continue to grow in size and move horizontally across the diagram (panel (a): red arrow). Low-power Mtype 1 double sources continuously grow until a distance of about 100 kpc where the jet becomes unstable and flaring. Mtype 3 dying sources with decreasing or terminating power will move downward in the diagram and end up with relics (panel (b)). Re-energized and intermittent Mtype 4 re-started sources will move upward into the standard evolutionary tracks ((panel (c)). Some low-power CSOs may evolve into Mtype  5 sources whose characteristic morphology is a hotpot within 1 kpc and a plume-like diffuse structure beyond the hotspot (panel (d)). Mtype  6 sources are shown as core–jet objects occupying the top left corner in the P– D diagram. Some Mtype  1 sources, which are shaped by the ram pressure of the IGM, are classified as Mtype  7 (panel (d)). All sources below the jet stability line are not able to evolve into Mtype 2 double sources (panel (a)).