Catalysis

The ninth entry is la limitation par le transport de matière, and the noun that opens it is a near-twin an English reader should hand back. With us « a limitation » is almost always a weakness. We speak of the limitations of a method, we are told to know our limitations, and the word carries a small apology inside it. French keeps la limitation for something else entirely, and for nothing shameful at all: the ceiling that has been imposed, the act of holding a quantity down. La limitation de vitesse is the speed limit on a road sign, la limitation des dépenses is a cap on spending, and la limitation par le transport de matière names the point at which supply, rather than chemistry, decides how fast a reaction can run. For the apologetic sense French reaches for the other noun, and reaches for it in the plural: les limites d’une méthode, connaître ses limites. The reading rule is one line long. Take la limitation as a cap that somebody or something sets, and les limites as the failings we were about to confess.