Ramadan, Islam's holiest month, begins at sundown on Wednesday, March 22, in the U.S. It ends with Eid al-Fitr on Friday, April 21.
Here is what you need to know about its significance, how Muslims observe the month and how non-Muslims can wish their friends and neighbors "Ramadan Mubarak."
What is Ramadan, and why is it important?
Ramadan is the ninth month of the Islamic calendar and is marked by fasting, reflection, charity and prayer.
It is believed that the first verses of Islam's holy scripture, the Quran, were revealed to the Prophet Muhammad during this time.
Is Ramadan the same time each year?
Ramadan is based on the lunar calendar, which consists of a 12-month year of approximately 354 days. This means each lunar month moves 11 days in the Gregorian calendar observed by the United States.
How do Muslims celebrate Ramadan?
The more than 2 billion observant Muslims around the world will engage in fasting from food, drink and sexual intercourse between dawn and sunset each day of the month, said Hussam Ayloush, the executive director of the Greater Los Angeles Area office of the Council on American-Islamic Relations.
Fasting is obligatory for Muslims, except for the ill, pregnant, traveling, elderly and/or menstruating, according to National Geographic.
These fasting periods can range from 11 to 16 hours per day. Before fasting each day, Muslims will begin with a pre-dawn meal called suhur, and then begin the fajr, the first prayer of the day, according to NatGeo. At dusk, after finishing the sunset prayer, or Maghreb, Muslims celebrate with the meal known as the iftar. This means "breaking the fast," and the meal is often shared with family and friends.
This ritual of daily fasting gives Muslims a period of spiritual reflection, Ayloush said.
"Being without food and drink throughout the day hopefully builds in us a kind of empathy where we feel very grateful for the blessing we receive from God ... and the way to show thankfulness is also by being empathetic who have less of these privileges," he said.
Muslims will also avoid negative acts like gossiping, lying and arguing during the month.
How do Muslims give charity during Ramadan?
Charity is a very important practice in Islam. During Ramadan, Muslims will often hold food drives or fundraisers to help the less fortunate.
What other rituals do Muslims perform during Ramadan?
Many Muslims will perform an extra prayer at night during Ramadan called taraweeh. They will also celebrate Laylat al-Qadr later in the month, which is the day many believe the Quran was first revealed.
How can non-Muslims greet their Muslim friends and neighbors during Ramadan?
Non-Muslims can wish Muslims "Ramadan Mubarak," which means "have a blessed Ramadan," Ayloush said.
"They can say, 'Happy Ramadan,' 'Joyful Ramadan.' Anything you can say would be greatly appreciated by your neighbors," he added.
When Ramadan is finished, Muslims will celebrate Eid al-Fitr, or the "Festival of the Breaking of the Fast." During this celebration, children receive gifts from family and friends. Muslims may also recite a special prayer during the morning of Eid, followed by a community celebration with food and games.