What characteristic describes a hypodermic needle?

A hypodermic needle is specifically designed to be attached to a syringe for the purpose of injecting substances into the body or withdrawing fluids from it. This characteristic is fundamental to its function, allowing healthcare providers to deliver medications or extract blood with precision and efficiency. The design of a hypodermic needle facilitates easy penetration into the skin and minimizes discomfort for the patient during the process.

While the other characteristics presented describe functions of different types of needles or methods of medication delivery, they do not accurately represent the primary function of a hypodermic needle. For example, needles used for oral medication are not hypodermic since they are designed for a completely different route of administration. Moreover, the size of a hypodermic needle can vary; it may be larger, but this is not a defining characteristic, as needle sizes and gauges are specific to the intended use. Lastly, while hypodermic needles can be used to withdraw blood, this is just one of many functions they serve, and not their primary defining feature.