principal focus - punching
- principal focus
- principal line
- principal lobe
- principal meridian
- principal plane
- principal point traverse
- principal point triangulation
- principal rafter
- principal scale
- principal sectorial area diagram
- principal volcano
- principle
- principle of action and reaction
- principle of conservation of energy
- principle of conservation of matter
- principle of continuity
- principle of design
- principle of duality
- principle of equivalence of mass and energy
- principle of least action
- principle of least squares
- principle of optimality
- principle of relativity
- principle of superposition
- print bar
- print chain
- print cycle
- print drum
- print position
- print routine
- print-works
- printed amplifier
- printed circuit
- printed circuitry
- printed electronic circuit
- printed form
- printed inductor
- printed wiring
- printed-circuit