Physical Symbols have Indeterminate Meaning

Consider a symbol: Δ

From the physical properties alone (such as length, width, height, the charge of the electrons, the wavelength of light it is giving out), you cannot tell if this symbol means "UFO", or "slice of pizza", or "dunce cap" or something else. Just the physical properties will not tell you what it means.

But appealing to further physical properties will be just as indeterminate as the original symbol, and will still not tell you what the symbol means.