How can two expressions have the same referent but different senses?

In the philosophy of language, the distinction between an expression's referent and its sense was famously articulated by the logician Gottlob Frege.12

The referent (Bedeutung) is the actual object or entity in the world to which an expression points. The sense (Sinn), by contrast, is the "mode of presentation" of that referent—the specific way in which the expression picks out or identifies that object.23

Because a single referent can be identified through multiple modes of presentation, two expressions can share the same referent while possessing different senses. For example:13

• The Morning Star and the Evening Star: Both expressions refer to the planet Venus, but they present it through different astronomical observations.14
• Everest and Chomolungma: These names refer to the same mountain, yet they present it via different cultural or geographic labels.2

This distinction explains why identity statements like "Everest is Chomolungma" can be informative, whereas "Everest is Everest" is trivial. Furthermore, it accounts for why substituting coreferring expressions in belief contexts can change a sentence's truth value; the sense determines how the subject is being thought about, not just who is being referenced.23