penumbra

noun

pen·​um·​bra pə-ˈnəm-brə How to pronounce penumbra (audio)
plural penumbrae pə-ˈnəm-(ˌ)brē How to pronounce penumbra (audio)
-ˌbrī
or penumbras
1
a
: a space of partial illumination (as in an eclipse) between the perfect shadow on all sides and the full light
b
: a shaded region surrounding the dark central portion of a sunspot
2
: a surrounding or adjoining region in which something exists in a lesser degree : fringe
the seventeenth century lay in the penumbra of the middle agesEdward Eggleston
3
: a body of rights held to be guaranteed by implication in a civil constitution
the penumbra of the Bill of Rights
4
: something that covers, surrounds, or obscures : shroud
a penumbra of secrecy
a penumbra of somber dignity has descended over his reputationJames Atlas
penumbral adjective

Did you know?

Every solar eclipse casts an umbra, the darker central area in which almost no light reaches the earth, and a penumbra, the area of partial shadow where part of the sun is still visible. Penumbra can thus be used to describe any "gray area" where things aren't all black and white. For example, the right to privacy falls under the penumbra of the U.S. Constitution; though it isn't specifically guaranteed there, the Supreme Court has held that it is implied, and thus that the government may not intrude into certain areas of a citizen's private life. Because its existence is still shadowy, however, the Court is still determining how much of an individual's life is protected by the right to privacy.

Examples of penumbra in a Sentence

the lunar eclipse began with a subtle darkening of the lunar surface as it passed within the Earth's penumbra a penumbra of despair fell over the doomed city
Recent Examples on the Web This occurs when the moon passes through the Earth’s partial shadow, or penumbra. Laura Baisas, Popular Science, 15 Mar. 2023 Penumbral lunar eclipse — March 25 The penumbra is formed when the sun, moon, and Earth are partially aligned, and Earth obstructs the sun's light to cover part of the moon in its shadow. Ria Gupta, Condé Nast Traveler, 6 Feb. 2024 The Moon’s penumbra first touches Earth at 11:42 a.m. EDT and last contacts it at 4:52 p.m. EDT. Michael E. Bakich, Discover Magazine, 22 Jan. 2024 This penumbral lunar eclipse will be more noticeable than past eclipses of this nature, as the entirety of the moon’s face will lie within Earth’s shadow, known as the penumbra. Stephanie Vermillion, Travel + Leisure, 1 May 2023 These stories, by a Canadian novelist, poet, and musician who died last year, peer keenly into the penumbra surrounding death. By Jessica Winter, The New Yorker, 19 June 2023 This less dramatic version of a lunar eclipse happens when the moon moves through the penumbra, or the faint, outer part of Earth’s shadow. Katie Hunt, CNN, 1 Mar. 2023 This full moon, which is classified as a strawberry moon, will bring a partial penumbral eclipse—in which the Earth's outer shadow, known as the penumbra, will appear on the moon's surface. Daisy Hernandez, Popular Mechanics, 5 June 2020 The Strawberry Moon will also showcase a penumbral lunar eclipse, which occurs when the moon passes through the Earth's penumbra, or partial shadow, causing part of the moon to look darker. Tierney McAfee, Country Living, 5 June 2020

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'penumbra.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

New Latin, from Latin paene almost + umbra shadow — more at umbrage

First Known Use

1665, in the meaning defined at sense 1a

Time Traveler
The first known use of penumbra was in 1665

Dictionary Entries Near penumbra

Cite this Entry

“Penumbra.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/penumbra. Accessed 19 Mar. 2024.

Kids Definition

penumbra

noun
pen·​um·​bra pə-ˈnəm-brə How to pronounce penumbra (audio)
plural penumbrae -brē How to pronounce penumbra (audio)
-ˌbrī
or penumbras
: the partial shadow surrounding a perfect shadow (as in an eclipse)
penumbral adjective

Medical Definition

penumbra

noun
pe·​num·​bra pə-ˈnəm-brə How to pronounce penumbra (audio)
plural penumbrae -(ˌ)brē How to pronounce penumbra (audio) -ˌbrī How to pronounce penumbra (audio) or penumbras
: a blurred area in a radiograph at the edge of an anatomical structure
penumbral adjective

Legal Definition

penumbra

noun
pe·​num·​bra pi-ˈnəm-brə How to pronounce penumbra (audio)
plural penumbras
1
: an area within which distinction or resolution is difficult or uncertain
the public-private penumbra
2
: an extension of protection, reach, application, or consideration
especially : a body of rights held to be guaranteed by implication from other rights explicitly enumerated in the U.S. Constitution
the First Amendment has a penumbra where privacy is protected from governmental intrusion Griswold v. Connecticut, 381 U.S. 479 (1965)
see also Griswold v. Connecticut
penumbral adjective

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