وفي الشرع: عبارة عما لزمنا من الأحكام ابتداء
Technically, azimah refers to the rulings imposed on us in the first instance.
In the first instance means that the ruling forms part of the original legal requirement, rather than a relaxation granted because of an extraordinary excuse. First identify the law's baseline obligation or prohibition; then ask whether the evidence grants a concession under the circumstances.
Azimah and rukhsah are therefore contrasted as the original operative rule and the qualified relief arising from a recognized excuse.