Ramadan is the ninth month of the Islamic calendar;[3] Muslims worldwide observe this as a month of fasting. This annual observance is regarded as one of the Five Pillars of Islam.[6] The month lasts 29–30 days based on the visual sightings of the crescent moon, according to numerous biographical accounts compiled in the hadiths. The word Ramadan comes from the Arabic root ramiḍa or ar-ramaḍ, which means scorching heat or dryness. Fasting is fardh ("obligatory") for adult Muslims, except those who are suffering from an illness, travelling, pregnant, breastfeeding, diabetic or going through menstrual bleeding. Fasting the month of Ramadan was made obligatory (wājib) during the month of Sha'aban, in the second year after the Muslims migrated from Mecca to Medina. While fasting from dawn until sunset, Muslims refrain from consuming food, drinking liquids, smoking, and engaging in sexual relations; in some interpretations Muslims also refrain from other behavior which could be perceived as sinful such as swearing, engaging in disagreements, backbiting and procrastination. Food and drink is served daily, before sunrise and after sunset. Spiritual rewards thawab for fasting are also believed to be multiplied within the month of Ramadan. Fasting for Muslims during Ramadan typically includes the increased offering of salat (prayers) and recitation of the Quran.