What is the defining feature of an ampule?

An ampule is characterized by its sealed glass container which typically features an elongated neck. This design allows for easy breakage to access the contents inside, which are usually sterile liquids. The elongated neck of the ampule provides a narrow point that can be snapped off, thus maintaining the sterility of the medication. This feature is essential for healthcare settings, especially when dealing with pharmaceuticals that must remain uncontaminated until usage.

The other choices do not accurately capture the essence of what defines an ampule. While disposability and being made of glass or plastic may be true for some ampules, these characteristics do not specifically define their unique structure. An open top is also not a feature of ampules, as they are sealed to protect their contents until they are ready to be used.