jealous: of God alone, fiercely unwilling to share his people's worship and devotion with any rival
This is a word the Bible reserves for God. It never describes a person. Its shape in Hebrew marks a fixed, defining quality rather than a passing mood, so it says something about who God is, not merely how he feels in a moment. And in every place it appears, it stands next to a command against worshiping other gods or bowing to idols. To call God jealous is to say he has bound himself to his people in a covenant and refuses to be treated as one option among many.
The difficulty is that the nearest English word, "jealous," has drifted toward petty suspicion and envy, which is not the idea here. The Bible's picture is closer to the rightful, protective love of a husband for his wife: a love that is wronged, not flattered, when devotion is given away to someone else. Because no single English word fits cleanly, translators reach for "jealous," "impassioned," or "zealous," and each captures part of the meaning while missing part of it.
The note that sounds through these passages is intensity, not insecurity. In Deuteronomy the same God is called a consuming fire in the very breath that calls him jealous, tying the word to burning seriousness rather than anxiety. His jealousy is the flip side of his commitment: he wants his people wholly, and he will act, even in judgment, against whatever pulls them away. In one passage this becomes his very name, so that jealousy is presented not as a flaw to excuse but as part of how God introduces himself.