Most often used Unicode math symbols and their mnemonic digraphs
Non-ASCII Unicode characters make text math notation more readable for everyone, but may not be easy either to enter or display correctly everywhere. Because of this the ASCII-only text math notation is recommended to be used whenever possible, especially for communicating math to many other people. If you have choice, the non-ASCII Unicode characters are recommended to be used only for your own notes and for communicating math to people who are able to display those characters correctly (which, is currently the typical case). For example, using non-ASCII Unicode characters can be recommended if, say, Vim or NeoVim is used by you and/or people (like us) to whom you communicate math. The Vim/NeoVim is universally available cross-platform text editor that supports mnemonic RFC1345 digraphs for convenient entry of most often used Unicode math symbols (digraph characters are to be typed in text editing mode after Ctrl+K) and, thus, is recommended for mathematical notes (and any text) exactly because of that feature (and many other good features).
¬ - NO - NOT SIGN ° - DG - DEGREE SIGN ± - +- - PLUS-MINUS SIGN × - *X - MULTIPLICATION SIGN ÷ - -: - DIVISION SIGN ϴ - '% - ACUTE ACCENT AND DIAERESIS (Tonos and Dialytika) ϵ - j3 - GREEK IOTA BELOW ‖ - !2 - DOUBLE VERTICAL LINE ′ - 1' - PRIME ″ - 2' - DOUBLE PRIME ‴ - 3' - TRIPLE PRIME ⁄ - /f - FRACTION SLASH ⁺ - +S - SUPERSCRIPT PLUS SIGN ⁻ - -S - SUPERSCRIPT MINUS ⁼ - =S - SUPERSCRIPT EQUALS SIGN ⁽ - (S - SUPERSCRIPT LEFT PARENTHESIS ⁾ - )S - SUPERSCRIPT RIGHT PARENTHESIS ₊ - +s - SUBSCRIPT PLUS SIGN ₋ - -s - SUBSCRIPT MINUS ₌ - =s - SUBSCRIPT EQUALS SIGN ₍ - (s - SUBSCRIPT LEFT PARENTHESIS ₎ - )s - SUBSCRIPT RIGHT PARENTHESIS ℃ - oC - DEGREE CENTIGRADE ℅ - co - CARE OF ℉ - oF - DEGREE FAHRENHEIT № - N0 - NUMERO SIGN ℗ - PO - SOUND RECORDING COPYRIGHT ℞ - Rx - PRESCRIPTION TAKE ℠ - SM - SERVICE MARK ™ - TM - TRADE MARK SIGN Ω - Om - OHM SIGN Å - AO - ANGSTROEM SIGN ← - <- - LEFTWARDS ARROW ↑ - -! - UPWARDS ARROW → - -> - RIGHTWARDS ARROW ↓ - -v - DOWNWARDS ARROW ↔ - <> - LEFT RIGHT ARROW ↕ - UD - UP DOWN ARROW ↖ - <!! - NORTH WEST ARROW ↗ - //> - NORTH EAST ARROW ↘ - !!> - SOUTH EAST ARROW ↙ - <// - SOUTH WEST ARROW ⇐ - <= - LEFTWARDS DOUBLE ARROW ⇒ - => - RIGHTWARDS DOUBLE ARROW ⇔ - == - LEFT RIGHT DOUBLE ARROW ∀ - FA - FOR ALL ∂ - dP - PARTIAL DIFFERENTIAL ∃ - TE - THERE EXISTS ∅ - /0 - EMPTY SET ∆ - DE - INCREMENT ∇ - NB - NABLA ∈ - (- - ELEMENT OF ∋ - -) - CONTAINS AS MEMBER ∏ - *P - N-ARY PRODUCT ∑ - +Z - N-ARY SUMMATION − - -2 - MINUS SIGN ∓ - -+ - MINUS-OR-PLUS SIGN ∗ - *- - ASTERISK OPERATOR ∘ - Ob - RING OPERATOR ∙ - Sb - BULLET OPERATOR √ - RT - SQUARE ROOT ∝ - 0( - PROPORTIONAL TO ∞ - 00 - INFINITY ∟ - -L - RIGHT ANGLE ∠ - -V - ANGLE ∥ - PP - PARALLEL TO ∧ - AN - LOGICAL AND ∨ - OR - LOGICAL OR ∩ - (U - INTERSECTION ∪ - )U - UNION ∫ - In - INTEGRAL ∬ - DI - DOUBLE INTEGRAL ∮ - Io - CONTOUR INTEGRAL ∴ - .: - THEREFORE ∵ - :. - BECAUSE ∶ - :R - RATIO ∷ - :: - PROPORTION ∼ - ?1 - TILDE OPERATOR ∾ - CG - INVERTED LAZY S ≃ - ?- - ASYMPTOTICALLY EQUAL TO ≅ - ?= - APPROXIMATELY EQUAL TO ≈ - ?2 - ALMOST EQUAL TO ≌ - =? - ALL EQUAL TO ≓ - HI - IMAGE OF OR APPROXIMATELY EQUAL TO ≠ - != - NOT EQUAL TO ≡ - =3 - IDENTICAL TO ≤ - =< - LESS-THAN OR EQUAL TO ≥ - >= - GREATER-THAN OR EQUAL TO ≪ - <* - MUCH LESS-THAN ≫ - *> - MUCH GREATER-THAN ≮ - !< - NOT LESS-THAN ≯ - !> - NOT GREATER-THAN ⊂ - (C - SUBSET OF ⊃ - )C - SUPERSET OF ⊆ - (_ - SUBSET OF OR EQUAL TO ⊇ - )_ - SUPERSET OF OR EQUAL TO ⊙ - 0. - CIRCLED DOT OPERATOR ⊚ - 02 - CIRCLED RING OPERATOR ⊥ - -T - UP TACK ⋅ - .P - DOT OPERATOR ⋮ - :3 - VERTICAL ELLIPSIS ⋯ - .3 - MIDLINE HORIZONTAL ELLIPSIS ⌂ - Eh - HOUSE ⌈ - <7 - LEFT CEILING ⌉ - >7 - RIGHT CEILING ⌊ - 7< - LEFT FLOOR ⌋ - 7> - RIGHT FLOOR ⌐ - NI - REVERSED NOT SIGN ⌒ - (A - ARC ⌕ - TR - TELEPHONE RECORDER ⌠ - Iu - TOP HALF INTEGRAL ⌡ - Il - BOTTOM HALF INTEGRAL 〈 - - RIGHT-POINTING ANGLE BRACKET ■ - fS - BLACK SQUARE □ - OS - WHITE SQUARE ▢ - RO - WHITE SQUARE WITH ROUNDED CORNERS ▣ - Rr - WHITE SQUARE CONTAINING BLACK SMALL SQUARE ▤ - RF - SQUARE WITH HORIZONTAL FILL ▥ - RY - SQUARE WITH VERTICAL FILL ▦ - RH - SQUARE WITH ORTHOGONAL CROSSHATCH FILL ▧ - RZ - SQUARE WITH UPPER LEFT TO LOWER RIGHT FILL ▨ - RK - SQUARE WITH UPPER RIGHT TO LOWER LEFT FILL ▩ - RX - SQUARE WITH DIAGONAL CROSSHATCH FILL ▪ - sB - BLACK SMALL SQUARE ▬ - SR - BLACK RECTANGLE ▭ - Or - WHITE RECTANGLE ▲ - UT - BLACK UP-POINTING TRIANGLE △ - uT - WHITE UP-POINTING TRIANGLE ▶ - PR - BLACK RIGHT-POINTING TRIANGLE ▷ - Tr - WHITE RIGHT-POINTING TRIANGLE ▼ - Dt - BLACK DOWN-POINTING TRIANGLE ▽ - dT - WHITE DOWN-POINTING TRIANGLE ◀ - PL - BLACK LEFT-POINTING TRIANGLE ◁ - Tl - WHITE LEFT-POINTING TRIANGLE ◆ - Db - BLACK DIAMOND ◇ - Dw - WHITE DIAMOND ◊ - LZ - LOZENGE ○ - 0m - WHITE CIRCLE ◎ - 0o - BULLSEYE ● - 0M - BLACK CIRCLE ◐ - 0L - CIRCLE WITH LEFT HALF BLACK ◑ - 0R - CIRCLE WITH RIGHT HALF BLACK ◘ - Sn - INVERSE BULLET ◙ - Ic - INVERSE WHITE CIRCLE ◢ - Fd - BLACK LOWER RIGHT TRIANGLE ◣ - Bd - BLACK LOWER LEFT TRIANGLE ★ - *2 - BLACK STAR ☆ - *1 - WHITE STAR ♀ - Fm - FEMALE SIGN ♂ - Ml - MALE SIGN ♠ - cS - BLACK SPADE SUIT ♡ - cH - WHITE HEART SUIT ♢ - cD - WHITE DIAMOND SUIT ♣ - cC - BLACK CLUB SUIT ♭ - Mb - MUSIC FLAT SIGN ♮ - Mx - MUSIC NATURAL SIGN ♯ - MX - MUSIC SHARP SIGN