[Agema]

A "basic" (i.e. all stats 10) human warrior costs 10gp. Pretty much anything cheaper tends to have stats deficiencies and could be thought of as militia. Velites, Fir Bolg and Huskarls are surely not militia.

It's a bit tougher to define in terms of nonhumans, but most army lists have a range of middling units with different equipment but the same stats who could be considered the "base" for that race (eg. Jotun javelinists/spearmen/axemen), and those that rate below are militia. You could otherwise identify militia by name, including terms like levy, thrall, slave and so on which also clearly imply inferior quality.