A constitutional amendment is a change to the constitution of a nation or a state. In jurisdictions with "rigid" or "entrenched" constitutions, amendments do not require a special procedure different from that used for enacting ordinary laws.
Some constitutions do not have to be amended with the direct consent of the electorate in a referendum. In some states a decision to submit an amendment to the electorate must first be taken by the legislature. In others a constitutional referendum may be triggered by a citizen's initiative. The constitutions of the Republic of Ireland, Denmark, Japan and Australia are amended by means of a referendum first proposed by parliament. The constitutions of Switzerland and of several states in the United States may be amended through the process of popular initiative.