- natural duality
- natural epimorphism
- natural equation
- natural equation of plane curve
- natural equivalence of functors
- natural extension
- natural extension mapping
- natural family of σ-field or natural filtration
- natural frame
- natural frame field
- natural frequency
- natural frequency of structure
- natural homomorphism
- natural homomorphism of a group
- natural homomorphism of Boolean algebras
- natural increasing process
- natural language processing
- natural language understanding
- natural logarithm
- natural logarithmic function
- natural logarithm table
- natural mapping
- natural method
- natural monomorphism
- natural number