The meaning of Substitute in dream | Dream interpretation
Dreams of a substitute reflect your level of flexibility as it relates to change and transformation. Perhaps you are grappling with feeling second best, an imposter, or that you are attempting to fill a void. Your dream may be giving you the message to be patient because in time sometimes the substitute or replacement, upon acceptance, turns out to be a blessing in disguise and maybe even better that the original.
(See Commutative contract)
Substitutions are used to compare similarities, add understanding, i.E. Name, title, an animal, etc.