| Subject | English | Thesaurus |
| abbr., law | C.B.O.E. | Chicago Board of Options Exchange |
| abbr., law | C.I.O. | Congress of Industrial Organization |
| abbr., insur. | C.O. | certificate of origin (c.o.) |
| abbr., commer. | C.O. | commercial operation |
| abbr., law | C.O.D. | Cash on delivery/Collect on delivery |
| abbr., f.trade. | C.t.I.O. | constructive total loss only |
| 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., law | E.E.O.C | Equal Employment Opportunity Commission |
| 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., law | I.C.O.R | Incremental capital-output ratio |
| abbr., law | O.C. | opere citato |
| abbr., law | O.C.A.S. | Organization Central American States |
| abbr., law | O.T.C. | over-the-counter |
| abbr., insur. | P O.C. | port of call |