The pieces of stone struck off a rock in the reduction sequence (flintknapping), each usually having a striking platform, bulb of percussion, and similar identifying features.
There are three main types of flakes:
Primary: A flake that has substantial amounts of cortex on it and that was one of the first flakes removed from the core when the stone was initially broken open.
Secondary: A flake that may have some cortex on its surface and that was removed during the rough shaping of a stone tool.
Tertiary: A flake that has no cortex on it and that was removed during the final shaping of a stone tool.