An airplane passenger moving 4 metres toward the rear of the plane has a displacement recorded as negative because:

1. A coordinate system must be chosen before any sign is meaningful. 2. In the system used, motion to the right is positive whereas motion to the left is negative. 3. The passenger's displacement is negative because his motion is toward the rear of the plane, in the negative direction of the coordinate system. 4. Had the axis been drawn the other way, the same motion would count as positive. 5. Distance, being a scalar magnitude, stays positive either way. _Source: OpenStax College Physics for AP(R) Courses 2e (CC BY 4.0), Ch 2 'Kinematics', sections 2.1-2.8_