capsule

American  

[kap-suhl, -sool, -syool] / ˈkæp səl, -sul, -syul /

noun

1. Pharmacology. a gelatinous case enclosing a dose of medicine.

2. Biology.

   1. a membranous sac or integument.

   2. either of two strata of white matter in the cerebrum.

   3. the sporangium of various spore-producing organisms, such as ferns, mosses, algae, and fungi.

3. Botany. a dry dehiscent fruit, composed of two or more carpels.

4. a small case, envelope, or covering.

5. Also called space capsule.  Aerospace. a sealed cabin, container, or vehicle in which a person or animal can ride in flight in space or at very high altitudes within the earth's atmosphere.

6. Aviation. a similar cabin in a military aircraft, which can be ejected from the aircraft in an emergency.

7. a thin metal covering for the mouth of a corked bottle.

8. a concise report; brief outline.

   An appendix to the book contains biographical capsules of the contributors.

---

verb (used with object)

capsuled, capsuling

1. to furnish with or enclose in or as if in a capsule; encapsulate.

2. to capsulize.

adjective

1. small and compact.

2. short and concise; brief and summarized.

   a capsule report.

3. containing only the most essential and versatile items of a particular kind.

   capsule wardrobe;

   capsule pantry.

capsule British  

/ ˈkæpsjuːl /

noun

1. a soluble case of gelatine enclosing a dose of medicine

2. a thin metal cap, seal, or cover, such as the foil covering the cork of a wine bottle

3. botany

   1. a dry fruit that liberates its seeds by splitting, as in the violet, or through pores, as in the poppy

   2. the spore-producing organ of mosses and liverworts

4. bacteriol a gelatinous layer of polysaccharide or protein surrounding the cell wall of some bacteria: thought to be responsible for the virulence in pathogens

5. anatomy

   1. a cartilaginous, fibrous, or membranous envelope surrounding any of certain organs or parts

   2. a broad band of white fibres ( internal capsule ) near the thalamus in each cerebral hemisphere

6. See space capsule

7. an aeroplane cockpit that can be ejected in a flight emergency, complete with crew, instruments, etc

8. (modifier) in a highly concise form

   a capsule summary

9. (modifier) (in the fashion industry) consisting of a few important representative items

   a capsule collection

---

capsule Scientific  

/ kăp′səl,-so̅o̅l /

1. A dry dehiscent fruit that develops from two or more carpels, as in the poppy and the cottonwood tree.

2. The sporangium (the hollow spore-producing structure) of mosses and other bryophytes.

3. The outer layer of viscous polysaccharide or polypeptide slime with which some bacteria cover their cell walls. Capsules provide defense against phagocytes and prevent the bacteria from drying out.

---

Other Word Forms

• uncapsuled adjective

Etymology

Origin of capsule

First recorded in 1645–55; 1950–55 capsule for def. 5; from French or directly from Latin capsula, equivalent to caps(a) “box” + -ula diminutive suffix; case ², -ule

Explanation

A capsule is a very small container that closes tightly. Many medicines come in capsules that can be easily swallowed. Certain brands of laundry or dishwasher soap can be bought in capsule form, and you might hide a secret note or special mementos in a time capsule. A biologist probably thinks of a capsule as an anatomical structure that encloses an organ. This, in fact, is the word's earliest meaning — in French, it's a "membranous sac," from the Latin capsula, "small box or chest."

Example Sentences

Then he could have released an image of himself in the Artemis space capsule and told us he’s an astronaut and he’s thinking of building a string of Trump hotels on the moon.

From Los Angeles Times • Apr. 13, 2026

The extreme heat meant the capsule, which the astronauts named Integrity, lost contact with mission control in Houston for six minutes during the descent.

From BBC • Apr. 11, 2026

They were also granted the honor of naming two moon craters — one after their moonship capsule Integrity and the other after Commander Reid Wiseman’s late wife Carroll.

From Salon • Apr. 11, 2026

The Apollo program relied on a single rocket, the Saturn V, which carried both the lunar lander and the capsule carrying the astronauts.

From Barron's • Apr. 11, 2026

Gagarin’s spinning capsule heated to a glowing red.

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

Related Words

• dose
• pellet
• pill