Alternative Writ or Optional Writ – command the defendant do a specified thing, or show why it has not been done or should not be done

Alternative Writ:

“(1827) A common-law writ commanding the person against whom it is issued either to do a specific thing or to show cause why the court should not order
it to be done.”[1]

Optional Writ:

“(18c) At common law, an original writ issued when the plaintiff seeks specific damages, such as payment of a liquidated debt. The writ commands the
defendant either to do a specified thing or to show why the thing has not been done.”

Also see Writ of Mandamus

References:

[1]: All definitions from: Black’s Law Dictionary Deluxe Tenth Edition by Henry Campbell Black & Editor in Chief Bryan A. Garner. ISBN: 978-0-314-62130-6

[2]: James L. High, A Treatise on Extraordinary Legal Remedies § 2, at 5-6 (1884).