| collaborative(adjective, communal, combined, shared, dual) |
| collected |
| collective(adjective, joint, united, linked, communal) |
| colluded(verb, co-operated) |
| combined(verb, adjective, fixed, involved, joint) |
| commensurate(adjective, close, equal, parallel, similar) |
| communal(adjective, combined, shared, dual) |
| compatible(adjective, close, equal, parallel, consistent) |
| complementary(adjective, like, parallel, similar, identical) |
| concerted(adjective, consistent, joint, harmonious, linked) |
| concomitant(adjective, similar, collateral, attendant, related) |
| concordant(adjective, joint, collateral, attendant, linked) |
| concurred(verb, co-operated) |
| conforming(adjective, close, equal, parallel, similar) |
| congruent(adjective, like, parallel, joint, identical) |
| conjoined |
| conjoint(adjective, joint, linked, combined, homogeneous) |
| conjunctive(joint, linked, combined, homogeneous, cooperative) |
| consanguinean |
| consistent(adjective, close, equal, parallel, similar) |