Unicode

Unicode symbols

Frequently used symbols:

Symbol	Unicode (hex)	Unicode (dec)	Keymap (linux be)	HTML entity	Unicode name	LaTeX
←	0x2190	8592	← `^AltGr-Y`	← `←`	Leftwards Arrow	`\leftarrow` `\gets`
↑	0x2191	8593	↑ `^AltGr-Shift-U`	↑ `↑`	Upwards Arrow	`\uparrow`
→	0x2192	8594	→ `^AltGr-I`	→ `→`	Rightwards Arrow	`\rightarrow` `\to`
↓	0x2193	8595	↓ `^AltGr-U`	↓ `↓`	Downwards Arrow	`\downarrow`
⃖	0x20D6	8406			Combining Left Arrow Above
⃗	0x20D7	8407			Combining Right Arrow Above
̅	0x0305	773			Combining Overline
̲	0x0332	818			Combining Low Line
∈	0x2208	8712			Element Of	`\in`
∉	0x2209	8713			Not An Element Of	`\notin`
∊	0x220A	8714			Small Element Of	`\smallin`
·	0x00B7	183			Middle Dot	`\cdotp` `\centerdot`

(LaTeX symbol name from package unicode-math)

How to find Unicode symbols:

shapecatcher.com - unicode character recognition — draw the symbol with the mouse to find it!
In Gnome, see character maps (gucharmap) to get unicode hex code.
In KDE, try KDE Character Selector (KCharSelect).
In Windows, try Character Map. Use Search for field to search characters with matching description (click Advanced view)

Using Combining symbols:

In Windows, try Character Map. Use Search for with Combining to find all combining symbols.
TBC

Reference:

unicode-math package (see unimath-symbols.pdf, also in LaTeX documentation)
Mathematical operators and symbols in Unicode (on wikipedia) (with explanation links for lots of symbols!)

These are similar to Windows' Alt-key code.

Ctrl-Shift-u, followed by unicode hexadecimal code while maintaining Ctrl-Shift (see [1])

Ex Ctrl-Shift-ue7 for ç, Ctrl-Shift-ue8 for è, Ctrl-Shift-ue9 for é...

Alt-KP0-Alt-KP9 — Press Alt key then the unicode character code in decimal.
4-digit hex code, then Alt-X — Type unicode character code in hexadecimal, then press Alt-X (at least in Office applications)