firmament

American  

[fur-muh-muhnt] / ˈfɜr mə mənt /

noun

1. the vault of heaven; sky.

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firmament British  

/ ˈfɜːməmənt, ˌfɜːməˈmɛntəl /

noun

1. the expanse of the sky; heavens

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Other Word Forms

• firmamental
  adjective

Etymology

Origin of firmament

1250–1300; Middle English < Late Latin firmāmentum sky, Latin: support, prop, stay, equivalent to firmā ( re ) to strengthen, support ( see firm ²) + -mentum -ment

Explanation

The firmament is the curve of the sky, especially if you imagine it as a solid surface. You can describe the sky at night as a firmament shining with stars (if you're feeling poetic). The word firmament comes from the Latin firmus, or "firm," and this description of the sky as something solid reflects ancient ideas of the way the universe was constructed. The first stargazers imagined the sky as a sphere, and it wasn't until the late 1500s that the idea of an infinite universe was seriously considered. Today the word firmament is mostly literary, used to poetically describe the visual curve of the sky.

Example Sentences

More than 60 years after her death, Monroe still glows brightly in the Hollywood firmament.

From Los Angeles Times • May 28, 2026

For those who grew up with Ms. Blume’s star fixed immutably in their literary firmament, it’s hard to think of her success as a fluke of time and place.

From The Wall Street Journal • Mar. 13, 2026

Not all of our stars are onscreen; more than two dozen are in the Michelin firmament.

From Los Angeles Times • Aug. 8, 2025

The cast - and the status of the 1922 original in the film firmament - means Eggers' movie had achieved a cult-like following even before its release.

From BBC • Dec. 31, 2024

All around her, in a firmament, soft white silkworms clung to bundled mulberry twigs.

From "Middlesex: A Novel" by Jeffrey Eugenides