twm: 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/twm - from package: xorg-x11-twm

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

On Debian possible default full paths are:

/usr/bin/twm - from package: twm

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

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