per

This term functions as a precise mathematical operator used to establish a ratio or a rate. It creates a direct link between two different units of measurement, ensuring that the value of the first is understood in relation to a single instance of the second. In professional and technical contexts, it is preferred over "a" or "an" (e.g., "miles per hour" instead of "miles an hour") because it eliminates ambiguity. It carries a clinical, objective tone, making it the standard for invoices, speed limits, and scientific data.