There are two types of law enshrined in constitutions. These are constitutional laws and ordinary laws. The procedure for amending ordinary laws is simple while the same for amending constitutional laws is difficult.
Constitutional laws are of fundamental importance, and they should not be frequently changed. Therefore in many countries very difficult procedures have been prescribed for amending them.
The American constitution was enforced in 1789. It is a very small constitution consisting of around 7000 words. But during this long period it has been amended only 27 times.
Amendment of any provision of constitution requires two-thirds majority support in both the House of Representatives and the Senate and its ratification by three-quarters of the states. The amendment of the German constitution requires two-thirds majority in both houses of the national legislature, namely, Bundestag and Bundesrat.
Some parts of the Indian constitution can be amended by simple majority in each house of the Parliament. But the amendment of several other provisions of the constitution requires special majority. The bill for amending these provisions has to be approved by special majority in each house of the Parliament and ratified by majority of the states.
The flexible constitution gives equal importance to constitutional laws and ordinary laws, and both kinds of laws can be amended in the same way. Any part of the constitution can be amended by simple majority of the members of national legislature.
In the words of Barker, the constitution which can be amended in an easy and simple manner as per the wishes of people is called the flexible constitution. Garner says that the flexible constitution is that constitution which does not enjoy more legal authority than ordinary law, and which can be changed like other laws.
The British constitution is the best example of flexible constitution. It can be amended by the British Parliament with simple majority.