under-

Beneath, under

e.g. underground, underneath, underpass

To go from one side to the other; to progress along a path

e.g. understand, undergo, underbear, undertake

Less than, beneath in quantity

e.g. underadditive, underage, underbound

Deficient, below what is correct, insufficient

e.g. underapply, underbill, underawe

Subordinate to

e.g. undersecretary, underling, underclass