ngettext: 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/ngettext - from package: gettext

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

On Debian possible default full paths are:

/usr/bin/ngettext - from package: gettext-base

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

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