Light, colour, surface

Le pouvoir couvrant of a paint is its opacity, and the phrase is worth more than its translation, because it is a mould rather than a single term. French takes le pouvoir — on its own the word for power in the political sense — sets a present participle behind it, and so names what a material is able to do. Le pouvoir absorbant belongs to a kitchen roll, le pouvoir isolant to a wall, le pouvoir sucrant to a sweetener, le pouvoir calorifique to a fuel, le pouvoir gonflant to a duvet. The frame is open: a laboratory that needs a name for a new property builds one on the spot, and every reader parses it at sight. English has to reach for a different noun each time — « opacity », « absorbency », « insulating value », « relative sweetness », « calorific value », « loft » — so the family is invisible in translation, six unrelated words for one idea. « Covering power » does exist in the paint trade, but as one term and not as a pattern. The mould was copied whole exactly once, in le pouvoir d’achat, « purchasing power ».