| Capacity development | GEO-7, GEO-1-6 |
| Capital | GEO-7, GEO-1-6 |
| Capital market | GEO-7 |
| Carbon dioxide removal | GEO-7, GEO-1-6 |
| Carbon fertilization | GEO-7, GEO-1-6 |
| Carbon intensity | GEO-7, GEO-1-6 |
| carbon lock-in | GEO-7 |
| Carbon market | GEO-7, GEO-1-6 |
| Carbon offset | GEO-7, GEO-1-6 |
| Carbon pricing | GEO-7, GEO-1-6 |
| Carbon sequestration | GEO-7, GEO-1-6 |
| Carbon sink | GEO-7, GEO-1-6 |
| Carbon tax | GEO-7, GEO-1-6 |
| Cascading use | GEO-7 |
| Cataracts | GEO-7, GEO-1-6 |
| CBDR | GEO-7 |
| Cellular agriculture | GEO-7 |
| Chikungunya | GEO-7, GEO-1-6 |
| Circular bioeconomy | GEO-7 |
| Circular economy | GEO-7, GEO-1-6 |
| Circular economy practices | GEO-7 |
| Circular economy principles | GEO-7 |
| Circularity | GEO-7 |
| Cities | GEO-7 |
| Citizen science | GEO-7, GEO-1-6 |
| Civil society | GEO-7, GEO-1-6 |
| Climate change | GEO-7, GEO-1-6 |
| Climate justice | GEO-7 |
| Climate variability | GEO-7, GEO-1-6 |
| Co-benefits | GEO-7, GEO-1-6 |
| Co-production | GEO-7 |
| Coastal zone | GEO-7, GEO-1-6 |
| Coastline | GEO-7, GEO-1-6 |
| Colonialism | GEO-7 |
| Community energy access | GEO-7 |
| Community engagement | GEO-7 |
| Complementarity | GEO-7, GEO-1-6 |
| Composting | GEO-7 |
| Consent | GEO-7 |
| Conservation | GEO-7, GEO-1-6 |
| Conservation agriculture | GEO-7 |
| Construction and demolition waste | GEO-7 |
| Consumer goods | GEO-7 |
| Consumer waste | GEO-7, GEO-1-6 |
| Consumerism | GEO-7 |
| Contaminant | GEO-7 |
| Coral bleaching | GEO-7, GEO-1-6 |
| Cost recovery | GEO-7 |
| Cover cropping | GEO-7, GEO-1-6 |
| Critical Energy Transition Minerals (CETMs) | GEO-7 |
| Critical Minerals | GEO-7 |
| Critically endangered | GEO-7, GEO-1-6 |
| Crop | GEO-7, GEO-1-6 |
| Cross-cutting issue | GEO-7, GEO-1-6 |
| Crusting | GEO-7, GEO-1-6 |
| Cryosphere | GEO-7 |
| Cultivated meat | GEO-7 |
| Cultural continuity | GEO-7 |
| Cultural heritage | GEO-7, GEO-1-6 |
| Cultural services | GEO-7, GEO-1-6 |
| Current trends | GEO-7 |
| Current trends scenario | GEO-7 |
| Cyclone | GEO-7, GEO-1-6 |