A leak is a way (usually an opening) for fluid to escape a container or fluid-containing system, such as a tank or a ship’s hull, through which the contents of the container can escape or outside matter can enter the container. Leaks are usually unintended and therefore undesired. The matter leaking in or out can be gas, liquid, a highly viscous paste, or even a solid such as a powdered or granular solid or other solid particles. Sometimes the word “leak” is used in a figurative sense. For example, in a news leak secret information becomes public.