Dim-witted and Subnormal

Dim-witted adjective - Not having or showing an ability to absorb ideas readily.

Subnormal and dim-witted are semantically related In some cases you can use "Subnormal" instead an adjective phrase "Dim-witted".

Subnormal adjective - Of a size that is less than average.

Dim-witted and subnormal are semantically related in limited topic. Sometimes you can use "Dim-witted" instead an adjective "Subnormal".