1. Can we find a definition for the circle in Affine space? 2.But can height in a triangle be defined in affine geometry?

Question

1. We know that an affine property is a property that does not involve lengths and angles. Typical examples are parallelism, and the definition of a tangent. But we don't know how we could define the circle.I thought it would be defined by the idea of infinity point, but I'm not exactly sure! Please tell me if this concept can be defined in affine geometry, which is based only on parallelism and points and vectors.
2. I know that the concept of perpendicularity is not defined in affine spaces. Then how could I define the height of a triangle? Or can't it be defined? Thanks !