**One triangle is isometric to another triangle if it has the same size and shape.** This means that it must have the same angles and side lengths as the other triangle.

Applying an isometric transformation to a triangle produces a new triangle that is isometric to the first. The isometric transformations are translation, which moves the triangle to a new position in the graph, reflection, which flips the triangle across a line, and rotation, which turns the triangle around the origin of the graph. A triangle that is produced by one of these transformations retains the size and shape of the original.