pigra

The loan and the build, standing side by side. Esperanto has two adjectives here and the difference between them is the whole design of the language in one line. Mallaborema is assembled: mal- reverses, labor- is work, -em- is inclined to, so it means disinclined to work - workshy, in exactly that English sense of a moral judgement about somebody's attitude to their job. Pigra is the plain international loan, and it says nothing about work at all. It says slow, unwilling to move, heavy. A pigra afternoon, a pigra dog by the stove, a pigra river.

So they are not interchangeable, though the dictionaries gloss both as lazy. If a colleague does not pull their weight, mallaborema is the accusation. If the whole town is dozing in the heat, pigra is the description. Where English uses one word for both, Esperanto lets you choose which claim you are making, and reaching for mallaborema when you meant "slow-moving" imports a criticism you may not have intended.

The second sense is the useful one. Pigra covers sluggish in the physical sense that English mostly reserves for water, engines and digestion: pigra fluo a sluggish current, pigra merkato a slack market, pigra stomako a lazy stomach. The adverb pigre does the same work - la horoj pasis pigre, the hours dragged.

Around the root. Pigreco is laziness as a quality, pigrulo a lazybones, pigriĝi to grow lazy, pigrigi to make somebody lazy. The opposite is diligenta, which is itself a loan, or laborema, which is the built one - and the pattern repeats: for most ideas Esperanto offers you a borrowed word and a transparent assembly, and both are correct.