In political science, an initiative (also known as a popular or citizens' initiative) is a means by which a petition signed by a certain minimum number of registered voters can force a public vote (plebiscite). The initiative may take the form of a direct initiative or an indirect initiative. In a direct initiative, a measure is put directly to a vote after being submitted by a petition. In an indirect initiative, a measure is first referred to the legislature, and then put to a popular vote only if not enacted by the legislature.