A "trigger mechanism" refers to a system or process that activates a specific response or action when certain conditions are met. This concept is commonly used in various fields, including psychology, engineering, and biology. For example, in psychology, a trigger mechanism might involve a stimulus that prompts an emotional reaction, such as a memory that causes anxiety. In engineering, a trigger mechanism can be a device that initiates a function, like the firing mechanism in a firearm. Similarly, in biology, it can refer to a biochemical process that starts a reaction, such as the release of hormones in response to stress.