|Expression: phrase, word, formula, or part of a formula. Below the level of sentences, therefore not true or false.|
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Expression: "The capital of the German Empire" (representing a proper name, meaning an object)
"Capital of the" unsaturated - "German Empire" saturated
Expression of a function: "The capital of x"
When we take as an argument the German Empire, we obtain Berlin as a function value.
An expression of a truth value does not assert anything yet.
Die Grundlagen der Arithmetik Stuttgart 1987
Funktion, Begriff, Bedeutung Göttingen 1994
Logische Untersuchungen Göttingen 1993