If the level of effective demand is much below the level of full employment equilibrium then which situation will appear in the economy?

Underemployment equilibrium

The equilibrium level of output may be more or less than the full employment level of output. If it is less than the full employment of output, it is due to the fact that demand is not enough to employ all factors of production.  This situation is called the situation of deficient demand and underemployment equilibrium. underemployment equilibrium refers to a situation when the aggregate demand is equal to the aggregate supply corresponding to the under-employment of resources. It occurs prior to the full employment level.