**Core Concept**
Subpoena is a legal document issued by a court or other authority to compel a person to testify or provide evidence in a legal proceeding. In the context of medical law, subpoenas are often used to summon medical professionals to testify as experts or to provide patient records.

**Why the Correct Answer is Right**
A subpoena is also referred to as a summons because it formally notifies the recipient of their obligation to appear in court or provide evidence. This terminology is used to emphasize the authoritative nature of the document and the recipient's duty to comply. The use of a summons highlights the legal weight of the subpoena and the potential consequences of non-compliance.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while a summons is a related legal concept, it is not the most commonly used synonym for subpoena.
**Option B:** Incorrect because a warrant is a different type of legal document used to authorize law enforcement to search or seize property or individuals.
**Option C:** Incorrect because a citation is a legal notice used to inform someone of a pending court action, but it is not a synonym for subpoena.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that medical professionals have a duty to comply with subpoenas and provide relevant information or testimony in court. Failure to comply can result in contempt of court charges and other legal consequences.

**Correct Answer:** C. Summons