The straight line is one of the five basic elements in Western
The straight vertical line stands for unity, oneness, the self (who am I?), the number 1, authority, power, the absolute, that which is outstanding, and contact between the lower and the higher.
When placed between other signs, has a demarcating and dividing meaning. In logic, for example, A B can mean either A or B, but not both.
In dualistic systems of meaning represents the positive pole. In the context of electrical power supply means power on, as opposed to for power off. As an electrical sign also denotes single-phase current.
In addition the short vertical line often signifies seriousness or danger, (as does ). The traffic sign is an example, as is in the ground-to-air emergency code, where it indicates that the pilot is badly wounded and in need of a doctor.