Hossein Kamaly is a professor at Barnard College who specializes in Islamic studies and Middle Eastern history. In an interview, he explained the basic tenets of Ramadan, the holiest month of the Muslim calendar, which begins on Monday for most of the world’s Muslims. The interview has been edited and condensed.

What is the significance of Ramadan? What is the event being observed?

All days may be equal on a secular calendar, but on religious calendars they are not: Some are more equal than others.

On the Muslim calendar, the entire month of Ramadan, the ninth month of the Arabic lunar calendar, marks the most special of all occasions. It is a celebration of the descent of the word of God, the Quran, from heaven to the earth.

During Ramadan, the gates of heaven are open wider than ever. Just as the word of God has come down, the word of supplicants goes up to God, more efficaciously than any other time.