⊖

⊖ is the Unicode character "circled minus" (U+2296) ⊖ may refer to:
 * Symmetric difference, the set of elements which are in either of two sets but not in their intersection
 * Erosion (morphology), one of the fundamental operations in morphological image processing
 * A function for reversal and rotation in the APL programming language
 * Symbol for the Escape character in ISO 2047