Hfrxdjt

I have been trying to typeset the character GREEK LETTER KOPPA. It has not been working. I know the Unicode number (U+03DE), and tried the command ^^3de and ^^3DE. Neither worked. I also tried char and char", but those didn't work either, other symbols get produced.

Does anybody have an idea as to how I can get my computer to typeset the symbol Ϟ?

MWE:

documentclass[a4paper, 12pt]article 
usepackage[ngerman, polutonikogreek]babel 
usepackage[T1]fontenc 
usepackage[utf8]inputenc 
usepackagearevmath 
usepackagelmodern 
fontfamilylmrselectfont 
usepackagegeometry 
 geometry 
 a4paper, 
 top=30mm, 
 left=25mm, 
 right=20mm, 
 bottom=20mm, 
 

begindocument 
selectlanguagengerman 

$Koppa$ 

enddocument

Using arevmath package you have the request symbol.

documentclassarticle
usepackagearevmath
begindocument

$Koppa$

enddocument

If you have a font on your system that you know has that character you can use a package such as fontspec or mathspec to typeset your document (either whole or part, as you prefer) in that font.

You have it in the cm-unicode fonts, to be used with xelatex. They also have the archaic koppa. If you can type it directly on your keyboard, XeLaTeX will understand it. Other than that I defined two commands to obtain them (note the hexadecimal code is not the official unicode hexadecimal number):

documentclass[12pt]article
usepackagefontspec
setmainfontCMU Serif
defkoppachar "03DF
defarchaickoppachar "03D9

begindocument

koppa: qquad LARGEkoppaqquad ϟ

normalsize archaic koppa: qquadarchaickoppaqquad ϙ


enddocument 

Here is one definition that works with the modern toolchain. It requires LuaLaTeX or XeLaTeX and an OpenType or TrueType font containing the glyph.

documentclass[varwidth]standalone
usepackagemathtools
usepackageunicode-math

defaultfontfeaturesScale = MatchLowercase 
setmainfontDejaVu Serif[Scale = 1.0]
setmathfontTeX Gyre DejaVu Math

newcommandkoppaifmmode%
mathordtext^^^^03deelse%
^^^^03defi

begindocument
Here is the symbol koppa.

( koppa = koppa_koppa_koppa )
enddocument

There are other ways to declare the symbol as well, including loading a font containing Ϟ as a symbol alphabet and using DeclareMathSymbol, or loading the symbol in text mode from a newfontfamily declared with fontspec, or defining it with newunicodechar, or loading all Greek letters from that Unicode block with ucharclasses, or finding an OpenType math font that has the glyph, or char"03DE, or symbol"03DE.

The problem was the includment of the polutonikogreek package. Without it, everything works just fine.