# var (2-var.us)

Var is short for variable. People use it to mean something that changes or differs, like weather or prices. It can also mean a particular thing in a particular case.

## What a model may hear
- variable declaration (JavaScript, programming): create a function-scoped variable with hoisting, not block-scoped like let or const
- variance (statistics, machine learning): measure spread or dispersion in data, or trade bias for variance in models
- value at risk (finance): calculate maximum expected loss at a confidence level for a portfolio
- virtual address register (computer architecture): refer to memory mapping hardware in CPU design
- /var directory (Unix/Linux systems): expect variable data files like logs, spools, and temporary runtime data

## Where people and models part ways
- Says: "Store this in var"
  Means: Save this value somewhere
  May be taken as: Declare a JavaScript variable with outdated scoping rules
  Say instead: "Save this value for later"
- Says: "Check the var"
  Means: See if the number changed
  May be taken as: Look for a variance calculation or inspect /var/log
  Say instead: "Check whether this value has changed"
- Says: "What's the var of this set?"
  Means: How much do these numbers differ?
  May be taken as: Compute statistical variance instead of simple range or standard deviation
  Say instead: "How spread out are these numbers?"
- Says: "Clean up the var"
  Means: Remove old changing data
  May be taken as: Delete system files in /var or clear all variables
  Say instead: "Remove old temporary data files"

## Tips
- Say 'variable' in full when you mean programming storage
- Say 'variance' in full for statistics to avoid finance or ML confusion
- Say 'spread' or 'range' if you do not need the technical statistical measure
- Specify the language when asking about code behavior: 'in JavaScript, what does var do?'
- Use 'changing value' or 'fluctuating amount' for everyday talk about things that vary

## Often confused with
- let: block-scoped declaration, preferred in modern JavaScript
- const: declaration that cannot be reassigned
- volatile: memory that may change unexpectedly, not just any variable
- parameter: input to a function, not a stored changing value
- attribute: property of an object, often fixed in structure
- variant: a distinct version or form, not a changing quantity