| deputy(noun, adjective, reserve, substitute, replacement) |
| stalwart(noun, reserve, substitute, fallback) |
| stand-in(noun, adjective, reserve, substitute, replacement) |
| support(prop, backbone) |
| assistant(noun, reserve, substitute, replacement, alternate) |
| double(noun, cover, reserve, substitute, replacement) |
| emergency(noun, adjective, increase, spare, reserve) |
| extra(noun, adjective, spare, reserve, replacement) |
| fill-in(noun, cover, reserve, substitute, replacement) |
| second(extra, substitute, replacement, auxiliary, supernumerary) |
| secondary(adjective, increase, reserve, subsidiary, supportive) |
| spare(noun, adjective, reserve, extra, replacement) |
| stand-by(noun, control, duty, reliable, responsible) |
| successor(noun, cover, reserve, substitute, replacement) |
| supplemental(adjective, increase, extra, auxiliary, supernumerary) |
| supplementary(adjective, increase, extra, auxiliary, supernumerary) |
| supporter(noun, support, prop, pillar, backbone) |
| ancillary(adjective, extra, substitute, auxiliary, supernumerary) |
| maintainer(support, prop, pillar, backbone, bulwark) |
| reliance |