Ramadan, the Islamic lunar month during which faithful Muslims throughout the world fast and offer special prayers, began Tuesday.

From sunrise to sunset throughout the month, adult men and women are expected to abstain not only from food and drink but from smoking and sexual intercourse as well.

Exempted from the fasting obligation are persons who are sick, who are traveling more than 50 miles during the day, and women who are pregnant or breast feeding. But they are expected to make up the days missed after Ramadan is over.

Also exempted are persons engaged in hard physical labor and the chronically ill. But they are expected to compensate for each day they cannot fast by providing one day's worth of food for a poor person.

Muslims who observe the fast usually begin their day before dawn with a substantial breakfast that includes plenty of liquids. Their big meal at night tends to be a small feast, which may include especially choice delicacies. "When you have only one [main] meal, you don't want to waste it on ordinary things," said Abdul Ahmed of the Islamic Center of Northern Virginia.

In Muslim tradition, Ramadan marks the time when the first revelations which have become the Koran were received by the Prophet Mohammed. It is a time for introspection and spiritual growth which the abstinence is intended to enhance.

In addition to fasting, faithful Muslims recite special prayers during Ramadan and are enjoined to concentrate on exemplary behavior, in obedience to the Prophet Mohammed, who said, "Whoever fasts but indulges in falsehood, let him know that his giving up of food and drinks shall not benefit him with God."