apertium-retxt: 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/apertium-retxt - from package: apertium

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

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