Minus sign inside a square box, a squared minus math operator; resembles a collapse button.
256 characters in the Mathematical Operators Unicode block.
U+2200FOR ALLU+2201COMPLEMENTU+2202PARTIAL DIFFERENTIALU+2203THERE EXISTSU+2204THERE DOES NOT EXISTU+2205EMPTY SETU+2206INCREMENTU+2207NABLAU+2208ELEMENT OFU+2209NOT AN ELEMENT OFU+220ASMALL ELEMENT OFU+220BCONTAINS AS MEMBERU+220CDOES NOT CONTAIN AS MEMBERU+220DSMALL CONTAINS AS MEMBERU+220EEND OF PROOFU+220FN-ARY PRODUCTU+2210N-ARY COPRODUCTU+2211N-ARY SUMMATIONU+2212MINUS SIGNU+2213MINUS-OR-PLUS SIGNU+2214DOT PLUSU+2215DIVISION SLASHU+2216SET MINUSU+2217ASTERISK OPERATORU+2218RING OPERATORU+2219BULLET OPERATORU+221ASQUARE ROOTU+221BCUBE ROOTU+221CFOURTH ROOTU+221DPROPORTIONAL TOU+221EINFINITYU+221FRIGHT ANGLEU+2220ANGLEU+2221MEASURED ANGLEU+2222SPHERICAL ANGLEU+2223DIVIDESU+2224DOES NOT DIVIDEU+2225PARALLEL TOU+2226NOT PARALLEL TOU+2227LOGICAL ANDU+2228LOGICAL ORU+2229INTERSECTIONU+222AUNIONU+222BINTEGRALU+222CDOUBLE INTEGRALU+222DTRIPLE INTEGRALU+222ECONTOUR INTEGRALU+222FSURFACE INTEGRALU+2230VOLUME INTEGRALU+2231CLOCKWISE INTEGRALU+2232CLOCKWISE CONTOUR INTEGRALU+2233ANTICLOCKWISE CONTOUR INTEGRALU+2234THEREFOREU+2235BECAUSEU+2236RATIOU+2237PROPORTIONU+2238DOT MINUSU+2239EXCESSU+223AGEOMETRIC PROPORTIONU+223BHOMOTHETICU+223CTILDE OPERATORU+223DREVERSED TILDEU+223EINVERTED LAZY SU+223FSINE WAVEU+2240WREATH PRODUCTU+2241NOT TILDEU+2242MINUS TILDEU+2243ASYMPTOTICALLY EQUAL TOU+2244NOT ASYMPTOTICALLY EQUAL TOU+2245APPROXIMATELY EQUAL TOU+2246APPROXIMATELY BUT NOT ACTUALLY EQUAL TOU+2247NEITHER APPROXIMATELY NOR ACTUALLY EQUAL TOU+2248ALMOST EQUAL TOU+2249NOT ALMOST EQUAL TOU+224AALMOST EQUAL OR EQUAL TOU+224BTRIPLE TILDEU+224CALL EQUAL TOU+224DEQUIVALENT TOU+224EGEOMETRICALLY EQUIVALENT TOU+224FDIFFERENCE BETWEENU+2250APPROACHES THE LIMITU+2251GEOMETRICALLY EQUAL TOU+2252APPROXIMATELY EQUAL TO OR THE IMAGE OFU+2253IMAGE OF OR APPROXIMATELY EQUAL TOU+2254COLON EQUALSU+2255EQUALS COLONU+2256RING IN EQUAL TOU+2257RING EQUAL TOU+2258CORRESPONDS TOU+2259ESTIMATESU+225AEQUIANGULAR TOU+225BSTAR EQUALSU+225CDELTA EQUAL TOU+225DEQUAL TO BY DEFINITIONU+225EMEASURED BYU+225FQUESTIONED EQUAL TOU+2260NOT EQUAL TOU+2261IDENTICAL TOU+2262NOT IDENTICAL TOU+2263STRICTLY EQUIVALENT TOU+2264LESS-THAN OR EQUAL TOU+2265GREATER-THAN OR EQUAL TOU+2266LESS-THAN OVER EQUAL TOU+2267GREATER-THAN OVER EQUAL TOU+2268LESS-THAN BUT NOT EQUAL TOU+2269GREATER-THAN BUT NOT EQUAL TOU+226AMUCH LESS-THANU+226BMUCH GREATER-THANU+226CBETWEENU+226DNOT EQUIVALENT TOU+226ENOT LESS-THANU+226FNOT GREATER-THANU+2270NEITHER LESS-THAN NOR EQUAL TOU+2271NEITHER GREATER-THAN NOR EQUAL TOU+2272LESS-THAN OR EQUIVALENT TOU+2273GREATER-THAN OR EQUIVALENT TOU+2274NEITHER LESS-THAN NOR EQUIVALENT TOU+2275NEITHER GREATER-THAN NOR EQUIVALENT TOU+2276LESS-THAN OR GREATER-THANU+2277GREATER-THAN OR LESS-THANU+2278NEITHER LESS-THAN NOR GREATER-THANU+2279NEITHER GREATER-THAN NOR LESS-THANU+227APRECEDESU+227BSUCCEEDSU+227CPRECEDES OR EQUAL TOU+227DSUCCEEDS OR EQUAL TOU+227EPRECEDES OR EQUIVALENT TOU+227FSUCCEEDS OR EQUIVALENT TOU+2280DOES NOT PRECEDEU+2281DOES NOT SUCCEEDU+2282SUBSET OFU+2283SUPERSET OFU+2284NOT A SUBSET OFU+2285NOT A SUPERSET OFU+2286SUBSET OF OR EQUAL TOU+2287SUPERSET OF OR EQUAL TOU+2288NEITHER A SUBSET OF NOR EQUAL TOU+2289NEITHER A SUPERSET OF NOR EQUAL TOU+228ASUBSET OF WITH NOT EQUAL TOU+228BSUPERSET OF WITH NOT EQUAL TOU+228CMULTISETU+228DMULTISET MULTIPLICATIONU+228EMULTISET UNIONU+228FSQUARE IMAGE OFU+2290SQUARE ORIGINAL OFU+2291SQUARE IMAGE OF OR EQUAL TOU+2292SQUARE ORIGINAL OF OR EQUAL TOU+2293SQUARE CAPU+2294SQUARE CUPU+2295CIRCLED PLUSU+2296CIRCLED MINUSU+2297CIRCLED TIMESU+2298CIRCLED DIVISION SLASHU+2299CIRCLED DOT OPERATORU+229ACIRCLED RING OPERATORU+229BCIRCLED ASTERISK OPERATORU+229CCIRCLED EQUALSU+229DCIRCLED DASHU+229ESQUARED PLUSU+229FSQUARED MINUSU+22A0SQUARED TIMESU+22A1SQUARED DOT OPERATORU+22A2RIGHT TACKU+22A3LEFT TACKU+22A4DOWN TACKU+22A5UP TACKU+22A6ASSERTIONU+22A7MODELSU+22A8TRUEU+22A9FORCESU+22AATRIPLE VERTICAL BAR RIGHT TURNSTILEU+22ABDOUBLE VERTICAL BAR DOUBLE RIGHT TURNSTILEU+22ACDOES NOT PROVEU+22ADNOT TRUEU+22AEDOES NOT FORCEU+22AFNEGATED DOUBLE VERTICAL BAR DOUBLE RIGHT TURNSTILEU+22B0PRECEDES UNDER RELATIONU+22B1SUCCEEDS UNDER RELATIONU+22B2NORMAL SUBGROUP OFU+22B3CONTAINS AS NORMAL SUBGROUPU+22B4NORMAL SUBGROUP OF OR EQUAL TOU+22B5CONTAINS AS NORMAL SUBGROUP OR EQUAL TOU+22B6ORIGINAL OFU+22B7IMAGE OFU+22B8MULTIMAPU+22B9HERMITIAN CONJUGATE MATRIXU+22BAINTERCALATEU+22BBXORU+22BCNANDU+22BDNORU+22BERIGHT ANGLE WITH ARCU+22BFRIGHT TRIANGLEU+22C0N-ARY LOGICAL ANDU+22C1N-ARY LOGICAL ORU+22C2N-ARY INTERSECTIONU+22C3N-ARY UNIONU+22C4DIAMOND OPERATORU+22C5DOT OPERATORU+22C6STAR OPERATORU+22C7DIVISION TIMES…and 56 more characters.