labor: work done for another, whether freely given or forcibly imposed
The word names human labor in its most fundamental sense: sustained effort directed toward a task on behalf of another party. Its range runs from Jacob's voluntary years of agricultural labor for his father-in-law to the crushing state-imposed bondage Israel endured in Egypt. What holds the range together is not the type of work but the relational structure: someone works for or under someone else. As Westermann observes in TLOT, the same relational logic governs the whole word family, the noun עֶבֶד (servant/slave), the verb עָבַד (to serve/work), and this action noun are all about the bond between a subordinate and a stronger party.
The forced-labor sense dominates in Exodus and Deuteronomy, where the word recurs as a Leitwort of Israel's suffering and of the deliverance narrative. Scholars from Sarna to Childs and Propp have noted that Exodus 1:14 alone packs three occurrences of the noun plus one of the related verb, a deliberate saturation effect. The phrase "hard service" (עֲבֹדָה קָשָׁה) becomes a fossilized formula: Deut 26:6 enshrines it as the credal description of Egypt, and Isa 14:3 reaches for the same phrase when describing future rest at Babylon's fall. Lam 1:3 stages the exile as a deliberate reversal of the Exodus, with the same word bearing the full weight of enslavement.