# semidiameter

> English word · Noun

## Definitions
1. The apparent radius of a star etc, when viewed from Earth.
2. A radius: half of a diameter.

## Etymology
From Middle English semidiametre, semydiametre, from Medieval Latin sēmidiameter, equivalent to semi- + diameter.

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