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• sac
  sac

  noun

  a baglike structure in an animal, plant, or fungus, as one containing fluid.
• Sac
  Sac

  noun

  Sauk.
• SAC
  SAC

  noun

  Strategic Air Command.

sac

¹ American  

[sak] / sæk /

noun

• sacs
  plural

1. a baglike structure in an animal, plant, or fungus, as one containing fluid.

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Sac ² American  

[sak, sawk] / sæk, sɔk /

noun

• Sacs,
  plural
• Sac
  plural

1. Sauk.

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SAC ³ American  

[sak] / sæk /

Or S.A.C.

noun

1. Strategic Air Command.

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sac ¹ British  

/ sæk /

noun

1. a pouch, bag, or pouchlike part in an animal or plant

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SAC ² British  

abbreviation

1. Special Area of Conservation

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sac Scientific  

/ săk /

1. A pouch or pouch-shaped structure in an animal or plant, often containing liquids. The human bladder is a sac.

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Other Word Forms

Derived Forms

• saclike
  adjective

Inflected Forms

Nouns

• Sac
  plural
• Sacs
  plural
• sacs
  plural

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Etymology

Origin of sac

First recorded in 1735–45; from Latin saccus “bag, sackcloth”; see sack ¹

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Explanation

A sac is a hollow space or container. While any pocket or pouch can be called a sac, the word usually refers to a small enclosed space that occurs in nature, like a spider's egg sac or a squid's ink sac. You might put your groceries in a sack, but without the “k” a sac is smaller and attached to a plant or animal. Human fetuses grow inside an amniotic sac, and seed plants produce pollen inside sacs as well. Since the mid-1700s, sac has been used to mean "biological pocket," from the Latin root word saccus, or "bag." If you’re not sure which sac to use, it’s almost always the other one unless you’re in biology class.

Example Sentences

See Examples For:

sac Sac SAC Sacs sacs

"It came right to the grass, right up above the curbs and flooded the whole cul de sac really."

From BBC ● Aug. 27, 2026

The larvae can alter the pH of the sac walls, causing the resilin to expand or contract.

From Science Daily ● Jul. 27, 2026

In a dark room, a doctor pointed to an hourglass shape glowing on the ultrasound screen: There was her amniotic sac, funneling into her dilated cervix, and there was their tiny daughter’s foot, dipping out.

From Salon ● May 27, 2026

Then came the worst part: I passed the amniotic sac.

From The Wall Street Journal ● May 13, 2026

“Yes, it is pretty,” replied Charlotte, patting the sac with her two front legs.

From "Charlotte's Web" by E.B. White

Now, Sac City sports 70 blooming creations, including entries from the Red Hats women’s group, the sheriff’s office—and the police.

From The Wall Street Journal ● Nov. 26, 2025

"We've got to flush this one down the toilet and get ready for Sac," said Kerr, whose side face the Sacramento Kings in their next match.

From BBC ● Jan. 21, 2025

Boys and girls cross country qualify for CIF Finals next Saturday at My Sac.

From Los Angeles Times ● Nov. 17, 2024

“Trump stood up for the people,” said Brett Potthoff, 30, an engineer from Sac City, Iowa, who considered caucusing for Mr. DeSantis but ultimately said he would support Mr. Trump.

From New York Times ● Jan. 21, 2024

“Omaha, Nebraska. Sac City, Iowa. Alexandria, Indiana. Darwin, Minnesota. Hollywood, California. Alliance, Nebraska. Okay. Those are the locations of all the things she—well, or whoever read this book—found interesting.”

From "Paper Towns" by John Green

Defra says it may not be necessary to make this area of maerl beds an SAC, "nor is there a requirement, to protect all examples of a species or habitats."

From BBC ● Jul. 31, 2026

Mount SAC, for instance, lost placements at multiple sites.

From Los Angeles Times ● Oct. 6, 2025

The situation has already led to limits being placed on housebuilding along SAC rivers.

From BBC ● Jun. 24, 2025

SAC Invitational, one of the most important high school cross-country events in California.

From Los Angeles Times ● Nov. 23, 2024

At the Air Force’s Strategic Air Command headquarters in Omaha, Nebraska, the SAC commander marched down a concrete ramp into the earth.

From "Fallout: Spies, Superbombs, and the Ultimate Cold War Showdown" by Steve Sheinkin

The Sacs and Fox mined and smelted 60 tons of lead for Shreve.

From Time Magazine Archive

A Mexican by birth, and interpreter for the Sacs and Foxes since 1858.

From Descriptive Catalogue of Photographs of North American Indians by W. H. Jackson

This led to later retaliation on the part of the French, but in the battle which was fought both sides lost heavily; and then both Sacs and Foxes fled from the country, never to return.

From Stories of the Badger State by Reuben Gold Thwaites

Several tribes, the Miamis, Sacs, and others, have claimed connection with the great chief; but it is certain that he was, by adoption at least, an Ottawa.

From The Conspiracy of Pontiac and the Indian War after the Conquest of Canada by Francis Parkman

He died, this last of the Sacs, poor, foolish old man, a few years later; and his bones, stolen for an Iowa museum, were cremated twenty years after in a fire which destroyed that institution.

From Historic Waterways?Six Hundred Miles of Canoeing Down the Rock, Fox, and Wisconsin Rivers by Reuben Gold Thwaites

Their secret is a remarkably durable system of air sacs that can tolerate far more pressure than researchers expected.

From Science Daily ● Jul. 27, 2026

In another chapter, Mr. Haskell follows the path of an owlet moth into the cranefly orchid’s flower and lets us watch how sacs of pollen attach themselves to the insect’s eye.

From The Wall Street Journal ● Apr. 17, 2026

The spiders’ white egg sacs, usually laid between October and November, are often attached to leaves, tree bark and flat structures and contain 400 to 500 eggs, according to Jorowatch.

From Los Angeles Times ● Apr. 9, 2026

However, identical twins can, and often do, develop in separate amniotic sacs.

From BBC ● Feb. 24, 2026

Male frigate birds with bright red balloonlike sacs under their chins cruised the shore.

From "Frightful's Mountain" by Jean Craighead George

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