Which of the following describes a capsule?

A capsule is specifically defined as a small, solid dosage form in which medication is encased within an outer shell, typically made of gelatin. This design allows for easy swallowing and provides a protective barrier for the medication, which can also aid in masking the taste. Capsules can be filled with powder, granules, or even liquid, depending on the formulation, and they dissolve in the digestive tract to release the medication.

Other options present different forms of pharmaceutical preparations. A thick paste for external application would refer more to creams or ointments, which are intended for topical use rather than ingestion. A liquid solution for inhalation would describe aerosolized medications used in devices like inhalers, which deliver medication directly to the lungs. A powdered form packaged for immediate use suggests a bulk powder that is often mixed with a liquid before administration, rather than a pre-formed encapsulated dosage. Each of these alternatives serves its own unique purpose in medication delivery, but they do not align with the definition of a capsule.