What is a thing that represents or stands for something else, especially a material object representing something abstract?

The correct answer is "symbol" because a symbol is a specific type of representation where a tangible object stands for an abstract concept or idea. For example, a dove often symbolizes peace, and a heart can represent love. Symbols are integral to literature, art, and various forms of communication, as they allow for deeper meanings to be conveyed through familiar representations.

In contrast, a signifier refers to a word or phrase that conveys meaning within the context of semiotics, but it does not inherently encompass the broader concept of representing abstract ideas through physical objects. Allegory, while involving representation, is a narrative technique where characters or events symbolize deeper moral or political meanings throughout a story, rather than focusing solely on material objects. A metaphor is a figure of speech that involves a direct comparison between two unrelated things to highlight similarities, but it does not involve the use of a physical object to represent an abstract concept. Thus, "symbol" is the term that most accurately describes the phenomenon of a material object standing for something abstract.