| conjecture | surmise |
| Conjecture abc | Abc conjecture |
| Conjecture de Birch et Swinnerton-Dyer | Birch and Swinnerton-Dyer conjecture |
| Conjecture de Hodge | Hodge conjecture |
| Conjecture de Mertens | Mertens conjecture |
| Conjecture de Poincaré | Poincaré conjecture |
| Conjecture de protection chronologique | Chronology protection conjecture |
| Conjecture de Scholz | Scholz conjecture |
| Conjecture de Syracuse | Collatz conjecture |
| Conjecture des nombres premiers jumeaux | Twin prime conjecture |
| Conjecture Monstrous Moonshine | Monstrous moonshine |
| Conjectures de Weil | Weil conjectures |
| conjoint | joint |
| conjointement avec | in conjunction with |
| Conjoints | Couple |
| conjonctif | subjunctive mood |
| conjonction | conjunction |
| conjonction de coordination | coordinating conjunction |
| conjonction de subordination | subordinating conjunction |
| Conjonction logique | Logical conjunction |
| conjonctive | conjunctiva |
| conjonctivite | conjunctivitis |
| conjoncture | picture |
| conjugaison | conjugation |
| conjugaison de postes | hookup |
| Conjugaison latine | Latin conjugation |
| conjugal | conjugal |
| conjuguer | conjugate |
| conjuguer les efforts | unite |
| Conjugué isogonal | Isogonal conjugate |
| conjurateur | conjurer |
| conjuration | abracadabra |
| Conjuration de Pison | Pisonian conspiracy |
| Conjuration des Pazzi | Pazzi |
| Conjuration Mineira | Inconfidência Mineira |
| conjurer | stave off |
| conjuré | conspirator |
| conjurée | conspirator |
| Conker | Conker the Squirrel |
| Conla | Connla |
| CONMEBOL | CONMEBOL |
| Conn Cétchathach | Conn of the Hundred Battles |
| Connacht | Connacht |
| Connacht Rugby | European Challenge Cup |
| Connad de Dalriada | Connad Cerr |
| connaissance | acquaintance |
