symbol glossary: ↔ if and only if i.e. is equivalent to ¬ negation i.e. not ⌜⌝ godel number https://people.clas.ufl.edu/jal/courses/mhf3202/symbols/ →, –>: implies, if … , then … . https://math.stackexchange.com/questions/1115066/meaning-of-symbols-vdash-and-models ⊢ the relation of derivability in a theory, meaning there is a formal derivation of a theorem from the axioms of the theory i.e. is derivable ⊨ the relation of logical consequence, meaning that a sentence in the language of the theory is true in all models of the theory, i.e. in all interpretations satisfying the axioms
.... this looks more accessible: https://qubd.github.io/files/TarskiUndefinability.pdf
