Full Idea
Theoretical reduction concerns terms found in a theory; Definitional reduction concerns concepts found in the mind; Ontological reduction is independent of how we conceptualize entities, or theorize about them, and is about reality.
Gist of Idea
Three types of reduction: Theoretical (of terms), Definitional (of concepts), Ontological (of reality)
Source
Jonathan Schaffer (Causation and Laws of Nature [2008], 1)
Book Reference
'Contemporary Debates in Metaphysics', ed/tr. Sider/Hawthorne/Zimmerman [Blackwell 2008], p.83
A Reaction
An Aristotelian definition refers to reality, rather than to our words or concepts.