Constancy

The state or quality of being constant or steadfast; freedom from change; stability; fixedness; immutability; as, the constancy of God in his nature and attributes.

Fixedness or firmness of mind; persevering resolution; especially, firmness of mind under sufferings, steadiness in attachments, or perseverance in enterprise; stability; fidelity.

(psychology) the tendency for perceived objects to give rise to very similar perceptual experiences in spite of wide variations in the conditions of observation

the quality of being enduring and free from change or variation; "early mariners relied on the constancy of the trade winds"

faithfulness and dependability in personal attachments (especially sexual fidelity)