Constantness vs. Constancy

Constantness and Constancy Definitions
Constantness
The state or quality of being constant.
Constancy
Steadfastness, as in purpose or affection; faithfulness.
Constancy
The condition or quality of being constant; changelessness.
Constancy
(uncountable) The quality of being constant; steadiness or faithfulness in action, affections, purpose, etc.
Constancy
(countable) An unchanging quality or characteristic of a person or thing.
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.
ADVERTISEMENT
Constancy
Fixedness or firmness of mind; persevering resolution; especially, firmness of mind under sufferings, steadiness in attachments, or perseverance in enterprise; stability; fidelity.
A fellow of plain uncoined constancy.
Constancy and contempt of danger.
Constancy
The quality of being free from change or variation
Constancy
The tendency for perceived objects to give rise to very similar perceptual experiences in spite of wide variations in the conditions of observation
Constancy
Faithfulness in personal attachment (especially sexual fidelity)