Per

Per is a preposition in English with several related senses. It commonly introduces a relation of rate or distribution, meaning “for each” or “for every,” as in miles per hour. It can also signify a means or channel (“by means of”) or indicate conformity with a standard or source (“as per” or “in accordance with”). The word is widely used in academic, scientific, legal, and technical writing to express proportional relationships and baselines concisely.

In rate and ratio expressions, per denotes division or a standardized quantity. For example, “60 miles per hour” means miles divided by hours, expressing a speed. In cost or quantity contexts, it links a quantity to its unit, as in “$3 per gallon.” Common phrases include per capita (per person), per annum (per year), and per diem (daily).

Other uses include formal or legal phrasing where per means “in accordance with” or “according to,” such as “as per your request” or “per the contract.” In this sense, per supplies a basis or reference for a statement or instruction. In everyday mathematics and science, per remains a compact way to express rates, densities, and proportions without repeating units.

Etymology traces per to Latin per, meaning through, by, or by means of. It entered English through Norman French and developed the modern sense of “for each” and “in accordance with” through usage in various technical and formal registers. The word remains a staple for succinct expressions of proportion, rate, and regulatory or methodological references.