8th Grade · Geometry
Preimage
8.G.A.1
Definition
The original figure before a transformation is applied. Its vertices are labeled with plain letters, while the transformed image uses primed letters.
Teach it
Where it is taught, with guided notes, practice, homework, an exit ticket and an interactive Teacher Deck.
Examples
- ABC is the preimage; A'B'C' is the image.
- Pre- means 'before' — the preimage comes first.
Key rule
The preimage is the input figure — the original, before any transformation.
Memory hook
The original, before anything happens to it.