Logical constant

https://en.wikipedia.org/wiki/Logical_constant

A logical constant of a language L is a symbol that has the same semantic value under every interpretation of L.

Two important types of logical constants are logical connectives and quantifiers. The equality predicate is also treated as a logical constant in many systems of logic.

One of the fundamental questions in the philosophy of logic is "What is a logical constant?", that is, what special feature of certain constants makes them logical in nature?

Some symbols that are commonly treated as logical constants are: T, F, ¬, ∧, ∨, →, ∀, ∃, =, ◻, ◊