# ionosphere

> English word · Noun · frequency rank #54,860

## Definitions
1. The part of the Earth's atmosphere beginning at an altitude of about 50 kilometers (31 miles) and extending outward 500 kilometers (310 miles) or more.
2. The similar region of the atmosphere of another planet.

## Etymology
From iono- + -sphere.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/ionosphere