U+27DA "⟚" Left and Right Double Turnstile Unicode Character

U+27DA "⟚" Left and Right Double Turnstile is a mathematical symbol used primarily in formal logic and model theory to represent a special type of logical consequence or entailment. It is visually distinct from the more common single turnstile (⊢) and the double turnstile (⊨), as it combines a left-pointing and a right-pointing double horizontal shaft with vertical bars at each end, often indicating a bidirectional or symmetric relationship of satisfaction or validity between logical statements. This symbol appears in advanced mathematical texts and research papers dealing with non-classical logics, substructural logics, or categorical logic, where it denotes a kind of logical equivalence or mutual entailment between two formulas under a given interpretation.