As the inevitable speculation begins in the wake of the shootings at a Sikh temple in Wisconsin on Sunday, it is important to note Sikhism is unrelated to Islam.

Sikhism -- also a monotheistic faith -- is believed to have more than 20 million adherents around the world and thought to have an estimated 250,000 of them in the U.S. It is considered to be the fifth-largest organized religion on the planet.

About 3,000 Sikh families live in southeastern Wisconsin, according to the Milwaukee Journal-Sentinel.

Sikhism was founded in the Punjab region of India in the 15th century by Guru Nanak Dev. Its most closely related organized religion may be Hinduism: One big difference between the two is that Sikhs are monotheistic (they believe in one god) and Hindus are polytheistic (they believe in multiple gods). Ik Onkar is a representation of the united of God in Sikhism.

Sikhism broke away from Hinduism in part because of the caste system in India that restricts social movements, according to the Huffington Post. The relative inflexibility of the caste system would be a concern for anyone who would want to marry someone from a different economic background, for example. Sikhs do not limit themselves in that way.

In fact, when Hindu leaders in the 14th century determined that people in the lower economic castes were "untouchables," they began showering whenever one of the poor people even touched them. One of the most important principles of Sikhism is that all people are equal, as noted by RealSikhism.com. Women have equal status and the same rights as men.  

Sikh temples are called gurdwara, which has various translations, such as "the gateway to the guru" or "the doorway to God." At the gurdwara, Sikhs are taught the simplest path to salvation is to live an honest life and meditate on God. In Sikhism, the equivalents of Western practices such as abstinence, fasting, and renunciation are not necessary to connect with God, according to RealSikhism.com. Sikhs also do not believe a church or house of worship is the best place to communicate with God.

Sikhs also encourage simple eating patterns, which mostly revolve around a vegetarian diet.

The BBC reported the ethics of Sikhism are based mainly on their scripture, the Guru Granth Sahib, and the Sikh Code of Conduct, the Rehat Maryada.

Although Sikh beliefs around euthanasia and suicide are not written in stone, Sikhs believe in most cases those practices work in opposition to God's plan.

The past decade in the wake of Sept. 11, 2001, terrorist attacks on America has not been the best of times for Sikhs in the U.S., in part because of the similarity in appearance of Muslims and Sikhs: For example, men of both faiths can have long beards and wear turbans.

Indeed, some members of the Wisconsin community of Sikhs victimized Sunday were subjected to harassment following the 9/11 terrorist attacks, according to Swarnjit S. Arora, a founder of the local Sikh Religious Society. In 2002, he told the Journal Sentinel, two taxis owned by Sikh drivers were vandalized and two Sikh men were assaulted in four separate incidents.