agent alternate alternative analogy backup change comparison copy counterfeit deputy double dummy elf child equal equivalent ersatz exchange fake fill-in ghost ghostwriter imitation locum tenens makeshift metaphor metonymy next best thing personnel phony pinch hitter proxy relief replacement representative reserves ringer second string secondary sign spares stand-in sub substituent substitute substitution succedaneum superseder supplanter surrogate symbol synecdoche third string token understudy utility player vicar vice-president vice-regent