gforth: command not found

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 Debian possible default full paths are:

/usr/bin/gforth - from package: gforth

You may install the required package with command apt-get install {package}

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