名詞 constancy:

1. the quality of being enduring and free from change or variation
   同義詞：stability
2. (psychology) the tendency for perceived objects to give rise to very similar perceptual experiences in spite of wide variations in the conditions of observation
   同義詞：perceptual constancy
3. faithfulness and dependability in personal attachments (especially sexual fidelity)

1. He is a husband of constancy.
   他是個(gè)忠貞不渝的丈夫。
2. He has constancy of purpose.
   他有堅(jiān)定不移的目標(biāo)。

con.stan.cy

n.（名詞）
Steadfastness, as in purpose or affection; faithfulness.
堅(jiān)定：（目標(biāo)或感情上的）堅(jiān)定不移；忠誠(chéng)
The condition or quality of being constant; changelessness.
始終如一：始終如一的情形或性質(zhì)；持久不變