one- - over
- operation and maintenance
- operation by hand
- operation factor
- operation of rolling
- operation of tube
- operation on slow wind
- operational procedure
- operational researches
- operational stroke
- operational versatility
- operator's cage
- operator's desk
- operator's pulpit
- opposed extrusion
- opposed hydraulic jack
- opposed striker
- opposed-blade shears
- opposing ram
- opposite poles
- opposite spin orientation
- opposite-flow
- opposition series generator
- optic axis of crystal
- optical activity
- optical differential dilatometer
- optical diffraction grating
- optical focus
- optical goniometer
- optical length
- optical magnification
- optical microscope observation
- optical microscopy methods
- optical multiplication
- optical pyrometer color pyrometer
- optical registration
- optical series
- optical strain gauge
- optics filming
- optimal cooling conditions
- optimal value