Which term signifies the representation or identification of something by a symbol?

The term that signifies the representation or identification of something by a symbol is "symbolise." This term specifically refers to using symbols to convey deeper meanings or to represent specific concepts, ideas, or objects. For instance, a dove often symbolizes peace, and a red rose can symbolize love. In contrast, the other choices refer to different modes of representation. "Express" typically involves conveying thoughts and feelings in a straightforward manner, while "depict" focuses on showing or portraying something in a visual format, often in art or literature. "Illustrate" generally means to clarify or explain something through examples or visuals, but it does not primarily emphasize the use of symbols in representation. Thus, "symbolise" is the most accurate term in this context.