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/6160ADB1D18B8D471766A6E1/61647BEC4A334378DE44ACA2/en_US/dc2c78d6e1888e9fe8a30068fc050f3f.png)