With languages, we aim to express what we think and feel. So understanding is the most important purpose of a language. But sometimes people don't want to be understood by everyone. In this case, they invent secret languages. Secret languages have fascinated people for thousands of years. Julius Caesar had his own secret language, for example. He sent coded messages to all areas of his empire. His enemies couldn't read the coded news. Secret languages are protected communication. We differentiate ourselves from others through secret languages. We show that we belong to an exclusive group. There are different reasons why we use secret languages. Lovers write coded letters at all times. Certain professional groups have their own languages as well. So there are languages for magicians, thieves and business people. But secret languages are most often used for political purposes. Secret languages have been used in almost every war. The military and intelligence services have their own experts for secret languages. Cryptology is the science of encoding. Modern codes are based on complicated mathematical formulas. But they are very difficult to decode. Without encoded languages, our life would be unthinkable. Encrypted data is used everywhere today. Credit cards and Emails – everything functions with codes. Children find secret languages especially exciting. They love to exchange secret messages with their friends. Secret languages are even useful for the development of children… They promote creativity and a feeling for language!