ctrans: 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 CentOS possible default full paths are:

/usr/bin/ctrans - from package: ncl

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/ctrans - from package: ncl-ncarg

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

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