de: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/var/spool/hylafax/bin/dict/de - from package: hylafax+

You may install the required package with command yum install {package}
Error in other languages:
de: bevel nie gevind nie
de: comandă negăsită
de: comando não encontrado
de: commande introuvable
de: command not found
de: käsku ei ole
de: không tìm thấy lệnh
de: komanda nerasta
de: Kommando nicht gefunden.
de: kommandot finns inte
de: komut yok
de: nie znaleziono polecenia
de: níor aimsíodh an t-ordú
de: no se encontró la orden
de: no s'ha trobat l'ordre
de: opdracht niet gevonden
de: parancs nem található
de: perintah tidak ditemukan
de: príkaz nenájdený
de: příkaz nenalezen
de: команда не найдена
de: командата не е открита
de: 命令找不到
de: コマンドが見つかりません