Sawm or Siyam is to mean total abstinence of food and liquid from dawn to dusk for one whole lunar month. For those who are married, they are to abstain from sexual relations during that time too.

Sawm (Fasting) takes place during the ninth month of the lunar calendar called Ramadhan. Sawm is one of the five pillars of Islam.

Total fasting is also a training process to attain self-restraint, self-control, self-discipline, self-obedience, self-education, and self-evaluation.

Few people are excused from fasting during Ramadhan. Some are required to make up later for the days they did not fast such as the travelers (over 50 miles by any means), sick, pregnant women, women nursing babies, and women during their periods. Other excused people are required to feed a poor person one meal for each day they do not fast if they can afford it, such as the elderly people and the ones who have permanent diseases like ulcers.

The main purpose of fasting is to attain the Taqwa-God-Conscious. Allah says:
O you who believe! Fasting is prescribed to you as it was prescribed to those before you that you may become God-Conscious. 2:183