# per (3-per.us)

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.

## What a model may hear
- 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

## Where people and models part ways
- Says: "per my last email"
  Means: as I already told you
  May be taken as: search for email metadata, thread analysis, or permission logs
  Say instead: "as I said in my last email"
- Says: "50 dollars per person"
  Means: each person pays fifty dollars
  May be taken as: compute a rate or divide by a variable named 'person'
  Say instead: "fifty dollars for each person"
- Says: "do this per the rules"
  Means: follow the rules
  May be taken as: look for a variable, function, or configuration named 'rules'
  Say instead: "do this following the rules"
- Says: "one per customer"
  Means: each customer gets one
  May be taken as: loop over customers with a limit of one iteration or apply a database constraint
  Say instead: "one for each customer"

## Tips
- Avoid 'per' when giving instructions; say 'for each' or 'according to' instead.
- Do not use 'per' as a variable name; it collides with common abbreviations.
- If you mean a rate, write the full formula so the model computes what you intend.
- Quote the phrase after 'per' to signal you mean natural language, not code.
- Check if the model interpreted 'per' as a command by asking it to restate your request in plain words.

## Often 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