An archaic, affectionate term for one's wife (equivalent to 'my dear' or 'honey' when addressing or referring to one's wife).
妻、今日はずっとそばにいてくれ。
My dear, please stay by my side all day today.
戦地へ赴く前に、彼は妻に手紙を書いた。
Before leaving for the front, he wrote a letter to his wife.