Context: Materialism belongs to the class of monist ontology. As such, it is different from ontological theories based on dualism or pluralism. For singular explanations of the phenomenal reality, materialism would be in contrast to idealism, neutral monism, and spiritualism.

Question: What class does materialism belong to?
Answer: monist ontology

Question: Why does materialism belong in monist ontology?
Answer: Unanswerable

Question: Monist ontology is the same as dualism and what else? 
Answer: Unanswerable

Question: Materialism is the same as idealism, neutral monism, and what else? 
Answer: Unanswerable

Question: What is the definition of neutral monism?
Answer: Unanswerable

Question: What is synonymous with dualism? 
Answer: Unanswerable