| 1 | English | complementary | Acting as a complement; making up a whole with... |
| 2 | English | complement | Something that completes; the consummation; The... |
| 3 | Latin | complementum | complement |
| 4 | Latin | compleō | — |
| 5 | Latin | cōn- | — |
| 6 | Latin | cum | with, along with; at; -fold |
| 7 | Old Latin | com | Alternative form of cum |
| 8 | Proto-Italic | kom | with, along, at |
| 9 | Proto-Indo-European | ḱóm | beside, near, by, with |
| 10 | Proto-Indo-European | ḱe | Deictic particle, here; Post-positional... |
| 11 | Middle English | kyt | — |
| 12 | German | kitt | — |
| 13 | Old High German | kuti | — |
| 14 | Proto-West Germanic | kwidu | gum, resin |
| 15 | Proto-Germanic | kweduz | resin |
| 16 | Proto-Indo-European | gʷet- | resin, gum; to say, speak |
| 17 | Proto-Indo-European | gū- | to bend; curve; arch; vault; to bow, bend, arch,... |