---
tag: 0ST21PGDAP
kind: concept
name: Almost surely
aliases: [almost-sure, with-probability-one]
msc: [60A05]
sources:
  - url: https://en.wikipedia.org/wiki/Almost_surely
    locator: lead section
same_as:
  wikidata: Q1434353
  wikipedia: Almost surely
---

## Summary

An event happens almost surely when its probability is $1$. The event can still fail for some outcomes, but these outcomes together have probability $0$.
The node [[almost surely|0R46A1XY60]] gives the precise definition.