Mathematical Operators
∀ ∀ for all, U+2200 ISOtech
∂ ∂ partial differential, U+2202 ISOtech
∃ ∃ there exists, U+2203 ISOtech
∅ ∅ empty set = null set = diameter, U+2205 ISOamso
∇ ∇ nabla = backward difference, U+2207 ISOtech
∈ ∈ element of, U+2208 ISOtech
∉ ∉ not an element of, U+2209 ISOtech
∋ ∋ contains as member, U+220B ISOtech (should there be a more memorable name than 'ni'?)
∏ ∏ n-ary product = product sign, U+220F ISOamsb (prod is NOT the same character as U+03A0 'greek capital letter pi' though the same glyph might be used for both)
∑ ∑ n-ary sumation, U+2211 ISOamsb (sum is NOT the same character as U+03A3 'greek capital letter sigma' though the same glyph might be used for both)
− − minus sign, U+2212 ISOtech
∗ ∗ asterisk operator, U+2217 ISOtech
√ √ square root = radical sign, U+221A ISOtech
∝ ∝ proportional to, U+221D ISOtech
∞ ∞ infinity, U+221E ISOtech
∠ ∠ angle, U+2220 ISOamso
∧ ∧ logical and = wedge, U+2227 ISOtech
∨ ∨ logical or = vee, U+2228 ISOtech
∩ ∩ intersection = cap, U+2229 ISOtech
∪ ∪ union = cup, U+222A ISOtech
∫ ∫ integral, U+222B ISOtech
∴ ∴ therefore, U+2234 ISOtech
∼ ∼ tilde operator = varies with = similar to, U+223C ISOtech (tilde operator is NOT the same character as the tilde, U+007E, although the same glyph might be used to represent both)
≅ ≅ approximately equal to, U+2245 ISOtech
≈ ≈ almost equal to = asymptotic to, U+2248 ISOamsr
≠ ≠ not equal to, U+2260 ISOtech
≡ ≡ identical to, U+2261 ISOtech
≤ ≤ less-than or equal to, U+2264 ISOtech
≥ ≥ greater-than or equal to, U+2265 ISOtech
⊂ ⊂ subset of, U+2282 ISOtech
⊃ ⊃ superset of, U+2283 ISOtech
⊄ ⊄ note that nsup, 'not a superset of, U+2283' is not covered by the Symbol font encoding and is not included.
  []   [] not a subset of, U+2284 ISOamsn
⊆ ⊆ subset of or equal to, U+2286 ISOtech
⊇ ⊇ superset of or equal to, U+2287 ISOtech
⊕ ⊕ circled plus = direct sum, U+2295 ISOamsb
⊗ ⊗ circled times = vector product, U+2297 ISOamsb
⊥ ⊥ up tack = orthogonal to = perpendicular, U+22A5 ISOtech
⋅ ⋅ dot operator, U+22C5 ISOamsb (dot operator is NOT the same character as U+00B7 middle dot)