id al-adha: the 10th day of Dhu'l-Hijja; all Muslims attend a service in the mosques and those who are not pilgrims perform a ritual slaughter of a sheep (commemorating God's ransom of Abraham's son from sacrifice) and give at least a third of the meat to charity
feast day: a day designated for feasting
molarity: concentration measured by the number of moles of solute per liter of solution