is an ancient philosophy that developed in Greece around 300 BC.
The main principle, or tenet, of Stoicism is that emotions lead people to make bad choices; if one can learn to view the world and relationships logically as opposed to emotionally, one would lead a more peaceful life.
The primary goal of the follower of Stoicism is to learn self-control where others might let their behavior be driven by emotional reactions, especially when faced with harmful emotions (anger, jealousy, envy, pride, etc.). The goal of the Stoic was to become an ethical and moral being that lived harmoniously with nature. Stoics believed that because all men were equal in nature, all men should be considered equal in life: The Emperor was not better than the common man, and the common man was not better than a slave.
Stoicism was popular throughout the Greece and the Roman Empire from its inception until 529 AD, when Roman Emperor Justinian I closed all philosophy schools in an attempt to expand Christianity throughout the world.
Today, the adjective stoic obviously has roots in the Stoic philosophy. A person who is described as stoic doesn't show his or her emotions, or lacks passion or feelings.