O/W - Class 516
OBG - Class 438
OBJECT - Classes 250, 353, 709, 718, 719
OBJECT (or SUBJECT) - Class 396
OBJECT HOLDER - Class 353
OBJECT OR ANALYTE - Class 378
OBJECTIVE - Class 396
ODE - Class 438
OED - Class 438
OEIC - Class 438
OF - Class 438
OIL - Classes 210, 428, 516
OISF - Class 438
OLEIC ACID; OLEATE - Class 516
OLEOPHILIC - Class 210
OLEOPHOBIC - Class 210
OMCT - Class 438
OMCVD - Classes 117, 438
OMVPE - Class 438
ONE-HOLE-CODE - Class 234
ONE-STROKE-STORAGE - Class 234
ONE-WAY BRAKE - Class 475
ONE-WAY CLUTCH - Class 475
OPEN LOOP CONTROL - Class 388
OPEN SEPARATOR - Class 171
OPERATING SYSTEM - Classes 709, 713, 718, 719
OPERATION - Class 226
OPERATOR - Class 049
OPERATOR* - Class 024
OPTHALMIC LENSES - Class 351
OPTICAL AXIS - Class 352
OPTICAL COMMUNICATION - Class 359
OPTICAL ELEMENT - Classes 356, 359, 372
OPTICAL FIBER - Classes 372, 385
OPTICAL MODULATION - Class 359
OPTICAL PATH - Class 351
OPTICAL SYSTEM - Classes 356, 359, 372
OPTICAL WAVEGUIDE - Class 385
OPTICS, OPTICAL - Classes 351, 356, 359, 372
OPTOMETRY - Class 351
OR - Class 425
ORANGE-PEEL - Class 037
ORBIT GEAR - Class 475
ORBITING - Class 065
ORD - Class 438
ORDERED - Class 438
ORGANIC - Classes 216, 424, 502, 504, 510
ORGANIC COMPOUND - Classes 204, 423, 520, 588
ORGANIC METAL CONTAINING COMPOUND - Class 588
ORGANIC SEMICONDUCTOR - Class 257
ORGANIC; ORGANIC COMPOUND; ORGANIC GROUP - Class 516
ORGANO-(prefix) - Class 516
ORGANOSOL - Class 516
ORIENTED-CRYSTAL - Class 117
ORIENTING - Classes 342, 343
ORIFICE - Class 072
ORIGINAL - Classes 355, 399
ORL - Class 438
OSA - Class 438
OSCILLATING - Class 366
OSCILLATING MOTION - Class 074
OSCILLATOR - Class 331
OSF - Class 438
OSMOSIS - Class 210
OTCR - Class 438
OTP - Class 438
OUTDIFFUSION - Class 438
OUTLET CLOSURE - Class 221
OUTPUT CIRCUIT - Class 323
OUTPUT CIRCUIT OR COUPLING - Class 330
OUTPUT MEMBER - Classes 060, 475
OUTPUT SHAFT: - Class 477
OVERDRIVE - Class 475
OVEREDGE STITCH - Class 112
OXIDANT - Class 210
OXIDANT COMPONENT: - Class 149
OXIDATION DYE - Class 008
OXIDE ISOLATION - Class 257
OXIDIZER - Class 060
OXO - Classes 260, 424
OXSEF - Class 438
OXY - Classes 260, 424