A tyrant (pronounce: tie-rant) is a person who rules with absolute power. In its Greek origin the word has no negative meaning: we translate Oedipus Tyranos as 'Oedipus the King'. A tyrant usually rules a country, and he often got his position as powerful ruler by force, although some of them inherited their power.
Later, the word came to mean someone who ruled with cruelty and injustice. The rule of a tyrant is called tyranny. The adjective is tyrannical.
When someone has power over everybody else so that nobody is allowed to question it, this is called absolute power. A tyrant rules by oppression. The people are oppressed (cruelly treated). A tyrant takes no notice of the wishes of the people, or of any constitutions (laws about how laws should be made).
In the 10th and 9th centuries BC, Ancient Greece was ruled by monarchs. By the 7th century BC, they were ruled by groups of aristocrats. These aristocrats started to become unpopular. This gave cruel people the chance to get power for themselves, telling the people that they would be good rulers, but turning bad once they got power.
Around 650BC the tyrant Cypselus became powerful in Corinth. There were other tyrants in the Asiatic countries that were ruled by Greece. Cypselus’s son Periander was also a cruel tyrant who ruled for 40 years. The tyranny in Corinth came to an end after he died.
Many tyrants of ancient Greece were supporters of the arts, but they always wanted art to show how wonderful they were, and no one could be critical of them.
There have always been tyrants in the world. Although there are more democracies nowadays, there still are countries which are governed by tyranny.