'Unfaithfulness' in the Bible

When Yahweh spoke at first by Hosea, Yahweh said to Hosea, "Go, take for yourself a wife of prostitution and children of unfaithfulness; for the land commits great adultery, forsaking Yahweh."

Indeed, on her children I will have no mercy; for they are children of unfaithfulness;

In the house of Israel I have seen something horrible; Ephraim's unfaithfulness [is] there. Israel is defiled.