Capsule

Capsule is a term used across several fields to denote a small container or a distinct module. The word comes from Latin capsula, a diminutive of capsa meaning 'box' or 'case'. In modern usage, capsule can refer to a pharmaceutical dosage form, a bacterial outer layer, or a type of spacecraft, among other senses.

In pharmacology, a capsule is a dosage form consisting of a shell that encloses an active ingredient. Hard capsules contain dry powders or pellets, soft capsules contain liquids or oils; shells are often gelatin but may be plant-based. They are designed for oral administration, offering dose precision and taste masking.

In microbiology, a capsule is a dense outer layer surrounding some bacteria and fungi, typically made of polysaccharides or proteins. It protects against desiccation and can enhance virulence by shielding organisms from immune defenses. Detection is often by special stains, and notable examples include Streptococcus pneumoniae.

In spaceflight, a capsule is a small spacecraft designed to survive atmospheric reentry and be recovered after landing. It usually features a heat shield and blunt body shape. Historical examples include Mercury and Apollo command modules, as well as Soyuz; contemporary examples include SpaceX Dragon and NASA's Orion.

Other uses include capsule hotels, which provide compact sleeping compartments; capsule wardrobes, a minimalist collection of interchangeable clothing; and capsule endoscopy, a medical procedure in which a patient swallows a camera-containing capsule to image the gastrointestinal tract.