The Full form of SOS is ‘Si Opus Sit’ which means ‘if needed’. SOS means a Morse code in old times which is used as a distress code to signal danger. The code signals that a person is in danger and needs immediate help. The SOS distress code is a sequence of three dots, three dashes and three dots without any space. In International Morse Code, three dots represent letter S and three dashes represent letter O. Historically, the code was used by the ships to signal danger later on it was associated with, Save Our Ship Or Save Our Souls, to remember the correct letters (SOS) of the code. So, in reality, SOS does not stand for anything. It was introduced by the German government on April 1, 1905 in radio regulations. It became the worldwide standard after it was included in the second International Radiotelegraphic Convention. It became effective on July 1, 1908. In 1999, this maritime radio distress signal was replaced by the Global Maritime Distress and Safety System.