| alternate(reserve, extra, substitute, subsidiary, auxiliary) |
| substitute(adjective, reserve, extra, alternative, subsidiary) |
| substitutive(reserve, extra, substitute, subsidiary, auxiliary) |
| acting(extra, auxiliary, supernumerary, back-up, flipside) |
| additional(extra, auxiliary, supernumerary) |
| adjuvant(reserve, subsidiary, supportive) |
| alternative(extra, auxiliary, supernumerary, back-up, flipside) |
| ancillary(extra, auxiliary, supernumerary) |
| another(extra, auxiliary, supernumerary) |
| appurtenant(reserve, subsidiary, supportive) |
| artificial(extra, auxiliary, supernumerary) |
| auxiliary(reserve, extra, subsidiary, supernumerary, supportive) |
| backup(reserve, extra, subsidiary, auxiliary, supernumerary) |
| counterfeit(extra, auxiliary, supernumerary) |
| dummy(extra, auxiliary, supernumerary) |
| emergency(reserve, subsidiary, supportive) |
| ersatz(extra, auxiliary, supernumerary) |
| experimental(extra, auxiliary, supernumerary) |
| extra(auxiliary, supernumerary) |
| false(extra, auxiliary, supernumerary) |