- national geodetic control network
- national geodetic network
- national height control net
- national leveling network
- national television system committee system
- natural balance
- natural block
- natural boundary condition
- natural boundary condition
- natural boundary of analytic function
- natural color photograph
- natural congruence
- natural constraint
- natural decomposition axiom
- 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