Ramadan, celebrated by 1.8 billion Muslims around the world and begins on Wednesday, March 22nd, takes place during the ninth month of the Muslim calendar and is a holy month of fasting. It begins and ends with the appearance of the crescent moon. The annual observance of Ramadan is regarded as one of the Five Pillars of Islam and lasts twenty-nine to thirty days, from one sighting of the crescent moon to the next. Islamic tradition states that it was during Ramadan, on the “Night of Power” (Laylat al-Qadr)—commemorated on one of the last 10 nights of Ramadan, usually the 27th night—that God revealed to the Prophet Muhammad the Qurʾān, Islam’s holy book, “as a guidance for the people.” For Muslims, Ramadan is a period of introspection, communal prayer, and reading of the Qurʾān.
A common method to wish a colleague, friend, or family member well during Ramadan is to say “Ramadan Mubarak” which translates to “Blessed Ramadan,” or “Ramadan Kareem” which translates to “Generous Ramadan” in English.
Original source can be found here.