| Subject | English | Thesaurus |
| abbr., f.trade. | B.O. | Bolivia |
| semicond. | Bi2O2Se | bismuth oxyselenide (MichaelBurov) |
| abbr., commer. | C.O. | commercial operation |
| abbr., insur. | C.O. | certificate of origin (c.o.) |
| abbr., law | C.O.D. | Cash on delivery/Collect on delivery |
| abbr., law | C.B.O.E. | Chicago Board of Options Exchange |
| abbr., law | C.I.O. | Congress of Industrial Organization |
| abbr., f.trade. | C.t.I.O. | constructive total loss only |
| abbr., f.trade. | d/o | deliver order |
| abbr., textile | D/O | direct order |
| abbr., insur. | D.O. | deferred ordinary share |
| abbr., insur. | D.O.C | endorsement drive other cars endorsement |
| abbr., insur. | D.O.C. | clause drive-other-cars clause |
| abbr., insur. | D.O.C. clause | drive-other-cars clause |
| abbr., insur. | D.O.C endorsement | drive other cars endorsement |
| abbr., f.trade. | d.I.O. | dispatch loading only |
| abbr., progr. | direct memory access I/O | DMA I/O (ssn) |
| abbr., progr. | direct memory access I/O | DMA input-output (ssn) |
| abbr., progr. | direct memory access I/O | direct memory access input-output (ssn) |
| abbr., progr. | direct memory access I/O | DMA input/output (ssn) |
| abbr., progr. | direct memory access I/O | direct memory access input/output (ssn) |
| abbr., f.trade. | D.T.O. | deep twist-off cap |
| abbr., law | E.O.E | errors and omissions excepted |
| abbr., law | E.O.M | end of month |
| abbr., law | E.E.O.C | Equal Employment Opportunity Commission |
| abbr., f.trade. | F.O. | forward order |
| abbr., f.trade. | F.O.C | free of charge (现略作 free) |
| abbr., insur. | F.O.C. | free of charge (f.O.C.) |
| abbr., insur. | F.O.T.f.o.t. | free on truck |
| abbr., insur. | F.O.T.f.o.t. | free on trail |
| abbr., insur. | F.O.T. | free on trail |
| abbr., f.trade. | f.O.W. | free on wagons |
| abbr., auto. | F.A.M.T.O. | first aid motor transport outfit |
| abbr., f.trade. | F.I.O. | in and out |
| abbr., law | F.I.O.S. | free in and out and stowage |
| abbr., polygr. | G.O. | gummed only |
| abbr., law | G.O.M. | Grand Old Man |
| abbr., law | G.O.P. | Grand old Party |
| abbr., polygr. | G.A.O.F. | gummed all over flap |
| abbr., f.trade. | G.P.O | general post office |
| abbr., IT | I/O | in-out |
| abbr., textile | I/O | value inorganic /organic value |
| abbr., f.trade. | I/O | in/out |
| abbr., f.trade. | I/O i.o. | inspection order |
| abbr., f.trade. | I/O i.o. | in order |
| abbr., publ.secur. | I.O.U. | due bill |
| abbr., f.trade. | I. P. O. | Irrevocable Purchase Order Bank Endorsed |
| abbr., law | I.C.O.R | Incremental capital-output ratio |
| abbr., law | IF/O | In favor of |
| abbr., insur. | J. W.O.B | jettison/washing overboard |
| abbr., law | J.N.O.V. | judgment non obstante veredicto |
| abbr., insur. | J.W.O.B. | jettison/washing overboard |
| abbr., f.trade. | L.O. | liaison office |
| abbr., law | LC.O.R. | incremental capital-output ratio |
| abbr., insur. | LT.O. | International Trade Organization |
| abbr., journ. | M.O. | makeover |
| abbr., photo. | M.O.D. | Minimum Object Distance |
| abbr., econ. | m-o-m | month on month |
| abbr., econ. | m.o.m. | middle of month |
| abbr., jewl. | Mississippi M.O.P. | Mississippi mother of pearl |
| abbr., econ. | M.P.O. | main post office |
| abbr., f.trade. | n/o | number |
| abbr., law | N.O.LN. | not otherwise indexed by name |
| abbr., law | N.O.R | notice of readiness |
| abbr., f.trade. | n.e.s.o.i | not elsewhere specified or included |
| abbr., busin. | O/A | open account trade |
| abbr., law | O.C. | opere citato |
| abbr., law | O.C.A.S. | Organization Central American States |
| abbr., f.trade. | O/D | overdraft or overdrawn |
| abbr., oil | O.F.M.E | Oil field machinery and equipment |
| abbr., f.trade. | O.F.S. | Orange Free State |
| abbr., textile | O-G | orange-green |
| abbr., polygr. | O.G. | Official Gazette of the United States' Patent Office |
| abbr., f.trade. | O.I. | optical index |
| abbr., f.trade. | O.K. | correct or approved (slang but now generally recognized) |
| abbr., polygr. | O.L. | open light |
| abbr., polygr. | O & M | Organization and Methods |
| abbr., econ. | O.&M. | organization and methods |
| abbr., telecom. | O&M center | operation and maintenance center |
| abbr., econ. | O.M.O. | ordinary money order |
| abbr., insur. | O.M.O. | overseas money order |
| abbr., mining. | O.M.S. | output per man shift |
| abbr., textile | O-NM | one-needle machine |
| abbr., auto. | o.p.m. | operation per minute |
| abbr., textile | O prc | our revised price |
| abbr., jewl. | o R | orange red |
| abbr., jewl. | O-ray | ordinary ray |
| abbr., textile | O/S | oxygen per unit of carbon black surface area |
| abbr., polygr. | O.S. | outer sheet |
| abbr., polygr. | O.S.O. | printed one side only |
| abbr., law | O.T.C. | over-the-counter |
| abbr. | O-va | all' ottava |
| abbr., mining. | O.W. | open work |
| abbr., jewl. | o Y | orange yellow |
| abbr., law | P.O. | postoffice |
| abbr., law | P.O. | Principal officer |
| abbr., textile | P&O | paints and oils |
| abbr., law | P.O. | police officer |
| abbr., insur. | P O.C. | port of call |
| abbr., insur. | P.O.D. | payable on demand |
| abbr., law | P.O.D | account payable on death account |
| abbr., textile | P-O-R | Product-O-Rail System |
| abbr., polygr. | p.t.o. | please, turn over |
| abbr., auto. | R&O | rust preventives and oxidation inhibitors hydraulic fluid |
| abbr., f.trade. | r. & o. | rail and ocean |
| abbr., oil | r.o.m. | run of mine coal |
| abbr., textile | S/O | shipper order |
| abbr., law | S.O. | Statutes of Ontario (Residential Tenancies Act 2006, S. O. 2006 C. 17 russiangirl) |
| abbr., publ.secur. | S.O.E. | special operations executive |
| abbr., f.trade. | S.O.P. | standard operation procedure |
| abbr., f.trade. | S.O.S | suspend other service |
| abbr., f.trade. | S.O.S | save our souls (ship) (Morse code signal for help) |
| abbr., insur. | S.O.S. | save our soul |
| abbr., law | S.R.O. | Statutory rules and orders |
| abbr., law | U&O | use and occupancy insurance |
| abbr., agric. | U.N.C.O.D. | Unites Nations Conference on Desertification |
| abbr., f.trade. | v.o.p. | value (as in) original policy |
| abbr., jewl. | y O | yellowish orange |