ntpq: 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/sbin/ntpq - from package: ntp

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

On Debian possible default full paths are:

/usr/bin/ntpq - from package: ntp

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

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