There is a prevailing conception of secularism and the absence of religious interference in government affairs, and vice-versa. While it is thought that there is no English word that captures the exact meaning of the french word "laïcité" which orignally comes from the Greek which means secular, it is in fact related to the English word laity or laymen, and "laicity" is the natural English spelling or rendering of the French term.
 There is a difference between laicity - a political theory aimed at separating politics and religion with the goal of promoting religious freedom - and secularism, in the sense of the declining importance of faith in individuals' daily lives (although the terms "secularism" and "secularity" are sometimes used in the sense described here). One who believes (or practices) laicism is a laicist.
The supporters of "laicity" argue that the term implies free exercise of religion, but no special status for religion: religious activities should be subject to the same set of laws as other activities and are not to be considered above the law. The government refrains from taking positions on religious doctrine and only considers religious subjects from their practical consequences on the inhabitants' lives. The critics, especially in regard to the Turkish version as well as recent ban of “hijab” in Europe , argue that this ideology is anti-religious and, in practice, restricts religious freedom.On the other side, supporters believe that it is the only way such different beliefs would not interfere with each other, hence helping the community to keep peace.

Countries constitutionally Secular (in the laic sense):

France
1st article of the 1958 constitution. The concept of laicity has been in the spotlight in the last years with controversial passing of laws which can be considered as anti-religion biased. They seem targeted to certain groups of the population and bring a feeling of limiting freedom in the country. These laws are directly related to a surge in terrorist attacks within the French territory.

United States
In the United States, the First Amendment to the Constitution contains a similar concept, although the term "laicity" is not used either in the Constitution or elsewhere. That amendment includes clauses prohibiting both governmental interference with the "free exercise" of religion, as well as governmental "establishment" of religion. These clauses have been held by the courts to apply to both the federal and state governments. Together, the "free exercise clause" and "establishment clause" are considered to accomplish a "separation of church and state."
However, separation is not extended to bar religious conduct in public places or by public servants. Public servants, up to and including the U.S. President, often make proclamations of religious faith. In contrast to France, the wearing of religious insignia in public schools is largely noncontroversial as a matter of law in the U.S.

Turkey
2nd article of the constitution. The Turkish word “laiklik” comes from the French word “laïque” (secular).

Mexico
3rd article of the 1917 constitution.

Portugal
Article 41, paragraph 4 of the 1978 constitution states that the state is secular. However, this is a relative secularity as the 1940 concordat with the Holy See kept its place the same as the law n°4 of August 21, 1971, often qualified as the law dealing with religious freedom, but reaffirms the special status of the Catholic Church. This law has been confirmed once again in 2004 when signed a new concordat with the Holy See.

India
42nd amendment of the 1947 constitution. The 1976 Constitution Act included the word “secular” in front of “democratic Republic”.

Japan
Article 20 of the Constitution of 1947. During the first half of the twentieth century, and particularly during the Thirties, the militarist regimes which controlled had imposed the “shintoïsme State”, following the traditional shintoïsme. Worked out and adopted during the American Occupation (1945-1952), the current Constitution integrates the Western designs of secularity and separation of the Church and the State.

Malaysia
Constitutionally Laic and is boasting religious liberty but only with non Moslems and with many discriminatory laws against other communities. With its double standards and two distinct courts, one federal and other religious, the constitution is all but secular. A simple example is the harassment case of a muslim lady (manager) who is prosecuted only because JAWI(the muslim court) could not prosecute the non-muslim owner of a book store.

Indonesia

Constitutionally Laic but religious identity is stated on official documents.