Being: essence and existence of entities
Existence: state of existing
Modality: possibility and necessity
Possibility: state of being possible
Necessity: state of being necessary
Reality: state of things as they are
Relationship: connection between entities
Change: alteration over time
Knowledge: understanding and awareness
Properties: characteristics of entities
Causality: cause and effect
Time: progression of events
Space: physical dimension
Mind: cognitive processes and thought
Body: physical aspect of entities
Ethics: moral principles and values
Agency: ability to act
Action: behavior and deeds
Rationality: logical and reasonable thinking
Justification: grounding and evidence
Value: worth and significance
Ontology: study of being and existence
Modal ontology: study of modality and existence
Modal metaphysics: study of possibility and necessity
Physical metaphysics: study of physical reality
Action theory: study of agency and action
Decision theory: study of rationality and decision
Causal metaphysics: study of causality and effects
Philosophy of time: study of time and change
Philosophy of mind: study of mind and consciousness
Epistemological metaphysics: study of knowledge and justification
Meta-ethics: study of moral value and justification.