In law, the word 'constitution' has two meanings:

1. a document, or a set of closely related documents, of special legal sanctity; and
2. a body of legal and political rules and arrangements concerning the government of the country.

According to Wheare, constitutions are classified as follows:

• written or unwritten.
The distinction between a written and unwritten constitution stresses the status of constitutional law rather than its dependence on oral custom as opposed to written documents.
You can discuss, at this point, a range of different systems including:
- the United Kingdom;
- Israel;
- Canada;
- New Zealand.
• flexible or rigid. This distinction concerns the way in which constitutional law is made, interpreted and amended.
• constitutions that are supreme over the legislature and those that are not.
In some contexts, it is assumed that those who draft written constitutions intend them to be the supreme law and that the legislature must act in a manner which is consistent with it. The traditional view is that in the United Kingdom Parliament is sovereign and that constitutional law is not supreme.
• constitutions based on separation of powers and those that are not.
Wheare admits that it is very difficult to find a constitutional system entirely based on the separation of powers.
• republican/monarchical constitutions.
Wheare suggests that the only practical point here is that republics usually have an elected president as head of state while monarchical constitutions have a hereditary monarchy.
• federations/unitary states.

In a unitary state all governmental power is concentrated in the organs of the central government. Their functions may, by legislation, be delegated to regional and/or local authorities. In a federation, independent states join together and empower the organs of central government while retaining residual sovereignty.