The degree of inclination for any structure or module indicates the amount by which it leans from a straight vertical line perpendicular to the earth's mean surface. For most structures the degree of inclination is 0°. If greater than zero, the degree of inclination can be deliberate (as in a building designed to lean) or accidental.

The reference is vertical at the structure's location. A fully upright structure has no inclination even when the ground alongside it slopes.

A positive inclination can describe an intended leaning form or an unintended lean. The angle alone does not identify the cause or establish whether the supporting structure is damaged.