Mental defectiveness and Subnormality

Mental defectiveness noun - Retardation sufficient to fall outside the normal range of intelligence.

Subnormality and mental defectiveness are semantically related. In some cases you can use "Subnormality" instead a noun phrase "Mental defectiveness".

Subnormality noun - The state of being less than normal (especially with respect to intelligence).

Mental defectiveness and subnormality are semantically related. Sometimes you can replace phrase "Mental defectiveness" with "Subnormality", this terms are similar.