constancy

nouns

the quality of being enduring and free from change or variation
"early mariners relied on the constancy of the trade winds"
is derived from
antonym
(psychology) the tendency for perceived objects to give rise to very similar perceptual experiences in spite of wide variations in the conditions of observation
faithfulness and dependability in personal attachments (especially sexual fidelity)
is derived from
is a type of (narrower)
the quality of being faithful