to serve: to do directed labor on behalf of someone or something, whether working the soil, laboring for a master, or worshiping a god.
This one word stretches from the most ordinary work to the highest act of worship, and that whole range is held together by a single idea: labor that is owed to and directed toward another. A farmer works the ground, a hired man works for a master, a conquered people works for a king, and a worshiper works for a god. In every case the worker belongs, for that work, to someone or something outside himself.
That is why the same word names both slavery and worship, which can seem strange in English. To the writers of the Hebrew Bible these were not opposite ideas but the same idea pointed in different directions. The question was never whether a person would serve, but whom. So the word carries no automatic sense of either degradation or honor; the context, and above all the one being served, decides which.
The Exodus story turns on exactly this. The same verb that describes Israel's brutal labor for Pharaoh describes the goal of their rescue: God tells Pharaoh to let the people go so that they may serve him instead. Leaving Egypt was not a move from service to freedom but from the wrong master to the right one. The later worship of the LORD at the sanctuary, and the warning against serving other gods, all draw on this single picture of a people who will always belong to someone.
Because the soil sense, the master sense, and the worship sense overlap so naturally, the standard reference works treat this as one word with a connected range rather than several unrelated words. The senses below mark out where along that range a given use sits, but they all share the one core of owed, directed labor.