A monarchy, (from the Greek monos, "one," and archein, "to rule") is a form of government that has a monarch as Head of State. The distinguishing characteristic of monarchies is that the Head of State holds their office for life, unlike in a republic, where a president is normally elected for a certain amount of time.
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"Kingdom" implies the existence of a king. Kings are bad. The most famous men to call themselves "king" during the past 1000 years were all torturers, murders and brutal enforcers of their will. The most famous ones, which I can think off the top of my head are:
King John-England
Ivan the Terrible-Russia
Louis XVI-France
Am I overacting in believing the use of "Kingdom" as a name by someone in a sports forum is really offensive and in bad taste? For those of you think that I am overreacting would your reaction be the same if someone was using "Fuhrer?"