General:
* Symbol: This is the most common term, but it implies a more abstract connection. A symbol can represent something else without necessarily being a direct replacement.
* Representation: This term emphasizes the idea of standing in for something else, but doesn't necessarily imply a shared meaning.
* Surrogate: This term indicates a substitute or stand-in, but doesn't necessarily imply a shared meaning.
More specific:
* Metaphor: This term implies a figurative comparison, where one thing is understood in terms of another.
* Allegory: This term refers to a story or extended metaphor that conveys a moral or symbolic meaning.
* Sign: This term indicates something that stands for something else, with a direct and often conventional relationship.
Other considerations:
* The nature of the shared meaning: Is it literal, figurative, cultural, personal, etc.?
* The relationship between the two things: Is it a direct replacement, a symbolic representation, a metaphorical comparison, etc.?
Example:
If you're talking about a red rose standing for love, you could call it a symbol, a representation of love, or a metaphor for love.
Ultimately, the best term depends on the specific context and the nuance of the relationship you want to express.