U+298B "⦋" Left Square Bracket with Underbar Unicode Character

U+298B "⦋" Left Square Bracket with Underbar is a punctuation mark used primarily in mathematical and formal notation, where it denotes a bracketing operation with a distinguishing underscore. It belongs to the Miscellaneous Mathematical Symbols-B block, introduced in Unicode 3.2, and is often employed in contexts such as interval notation or specialized algebraic expressions to indicate a half-open boundary or a variant bracket function. Its design combines a standard opening square bracket with a horizontal line extending from the bottom of the left vertical stroke, giving it a distinct visual cue that separates it from more common bracket forms.