A square is an aspect centered on 90°, one quarter of a circle. A chart’s orb rules determine which near-90° separations receive the label.
Astrology commonly reads a square as friction, effort, or pressure to adjust how two symbolic functions operate together. “Challenging” is not the same as harmful or doomed; it is a reflective theme rather than a prediction.
The 90° separation is geometry. The orb and interpretation are declared conventions. A trine uses a 120° target and is traditionally described with a different vocabulary, but neither type ranks a person or guarantees an outcome.