per

The word "per" is a Latin preposition originally meaning "through" or "by." While its original sense of "moving through" isn't as common in everyday English today, it has evolved into several important meanings primarily relating to rates, ratios, and specific instructions. Most often, you'll encounter "per" signifying for each or in relation to.

Imagine a baker selling cookies for $2 per cookie—that means each individual cookie costs two dollars. This is its most common usage: expressing a quantity or rate in connection with one unit of something else. You'll see it frequently when discussing prices (cost per item), speed (miles per hour), measurements (inches per year), and financial periods (10% interest per annum).

However, "per" isn't limited to just numbers. It is also used in a formal way to indicate "according to" or "in accordance with." For example, "As per your request..." means according to what you asked for. This usage is common in business correspondence and legal documents. You might also hear it in specialized Latin phrases that have entered English, such as "per capita," meaning "for each person," or "per se," meaning "by itself."

Sometimes, "per" can even subtly suggest a specific method or standard. If a technician says a task was performed "per protocol," they mean it was done exactly as the rules dictated.

So, whether you're calculating costs, giving formal instructions, or describing rates and ratios, "per" is a versatile tool that helps us understand how things relate to each other—one unit at a time.