(psychology) the tendency for perceived objects to give rise to very similar perceptual experiences in spite of wide variations in the conditions of observation(noun.cognition)
faithfulness and dependability in personal attachments (especially sexual fidelity)(noun.attribute)
source: wordnet30
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.(noun)