[историческое]; сокращение от Soviet Union Советский Союз
(Standard Unit) стандартный сегмент конструктива (25 мм)
сокращение от strontium unit стронциевая единица (дозы излучения)
(substitute user) The Unix command which allows you to become another user after entering their password. su is most often used without arguments in which case it defaults to user root. Some versions of Unix only allows this command to be used by members of the wheel group.