As you begin to research using security printing to secure your product or documents, you will hear a lot of terms being tossed around.
![twenty euro banknote under ultra-violet light](https://i0.wp.com/wellsdrew.com/wp-content/uploads/2022/09/euro1022014-300x199-1.jpg?w=800&ssl=1)
Two terms commonly used are Covert and Overt. Similar words with opposite meanings.
Covert simply means a hidden image invisible to the naked eye. An example of a covert image would be one printed with invisible UV inks that fluoresce under UV light. The example in this picture is a €20 banknote under ultraviolet light