Keyframe
A control that denotes the value of a video or audio effect setting at a particular point in the timeline. When two keyframes with different values are set, a transition from one value to another is calculated, resulting in a dynamic change to that setting. In Final Cut Pro, you add keyframes (diamonds) to a clip in the keyframe editor, then adjust their values in the inspector.
![The timeline with the keyframe editor open, showing two keyframes added to the Opacity setting in a clip.](https://help.apple.com/assets/64F8D8B5067449DAC109C68E/64F8D8B8067449DAC109C694/en_US/3245f37219712c0332ac482368b36f7a.png)