Opposition
In plain words
Two planets at opposite ends of the sky, facing each other across the circle. You feel this as two pulls that both want the whole day, and it often arrives through another person.
In the tradition's terms
180° apart: the two ends are in full view of one another, which makes an opposition the most conscious of the hard angles.
In depth
Separation 180°. The axis is visible from either end, so it is read as projection — the half you will not own turns up wearing somebody else's face.