A quick-reference glossary of the terms that appear most often in mandamus petitions and court opinions.

Mandamus filings are full of specialized vocabulary. This glossary collects the terms that come up most frequently across the articles on this site.

Petitioner and respondent

The person or entity filing the mandamus action is the petitioner. The government official, agency, or court being asked to act is the respondent. This differs from the "plaintiff" and "defendant" labels used in most ordinary civil lawsuits.

Alternative writ and peremptory writ

An alternative writ orders the respondent either to perform the act or to appear in court and explain why it should not have to. A peremptory writ is a final, unconditional order to perform the act, typically issued after the respondent has had a chance to respond.

Ministerial duty

A duty so clearly defined by law that the official has no discretion in how to carry it out — discussed in detail elsewhere in this section.

Show cause order

A court order requiring the respondent to appear and explain, or "show cause," why the requested writ should not be granted.

Return

The respondent's formal written answer to a mandamus petition, addressing the facts and legal arguments raised.

Relator

In some jurisdictions, particularly for original proceedings in appellate courts, the petitioner is referred to as the "relator" — the party on whose behalf the writ is sought.

TRAC factors

A six-factor test, drawn from the case Telecommunications Research & Action Center v. FCC, that many courts use to evaluate claims of unreasonable agency delay.

Sua sponte

A Latin phrase meaning a court acts "on its own motion," without a request from either party — relevant when courts raise standing or jurisdictional issues themselves.