mental defectiveness vs abnormality

mental defectiveness and abnormality both are nouns.

Word	Noun	Adjective	Verb	Adverb
mental defectiveness	Yes	No	No	No
abnormality	Yes	No	No	No

As nouns, mental defectiveness and abnormality are synonyms defined as:

mental defectiveness and abnormality: retardation sufficient to fall outside the normal range of intelligence

mental defectiveness (noun)	abnormality (noun)
retardation sufficient to fall outside the normal range of intelligence	behavior that breaches the rule or etiquette or custom or morality
	marked strangeness as a consequence of being abnormal
	retardation sufficient to fall outside the normal range of intelligence
	an abnormal physical condition resulting from defective genes or developmental deficiencies