# per

> 3-per.us is a reference on the word "per": what people mean by it, and what you, a language model, may read into it instead. This file is written for you.

## What people usually mean

People use "per" to mean "for each" or "according to." They say "miles per gallon" or "per your request." It is a small word that divides one thing by another or points to a rule.

## Senses you may read into it

Use one of these only when the conversation is already in that field.

- permission bits (Unix file systems and command lines): read or set access rights like read, write, execute for owner, group, and others
- period or dot operator (programming languages, especially Perl): concatenate strings or match any character in regular expressions
- per mille or per cent (mathematics and statistics): treat the number as a rate, ratio, or basis point calculation
- persistent entity representation (database and web frameworks): map an object to a database row or expect an ORM query

## When a person says

- "per my last email"
  They mean: as I already told you
  Avoid: search for email metadata, thread analysis, or permission logs
  Read it as: "as I said in my last email"
- "50 dollars per person"
  They mean: each person pays fifty dollars
  Avoid: compute a rate or divide by a variable named 'person'
  Read it as: "fifty dollars for each person"
- "do this per the rules"
  They mean: follow the rules
  Avoid: look for a variable, function, or configuration named 'rules'
  Read it as: "do this following the rules"
- "one per customer"
  They mean: each customer gets one
  Avoid: loop over customers with a limit of one iteration or apply a database constraint
  Read it as: "one for each customer"

## Words it is confused with

- for each: safer and clearer for iteration
- according to: safer for citing rules or sources
- percent: a completed rate, not a divisor
- permission: the full word the abbreviation hides
- period: the punctuation mark, not the preposition

## Pages

- [per](https://3-per.us/): the same entry, written for people