Jewish practices vary between denominations in the details and rigorousness of their observance. Shabbat, or Sabbath, is the weekly day of rest from sundown Friday to sundown Saturday, during which observant Jews attend synagogue and refrain from work. Prayer recitations generally occur three times a day, with a fourth on Shabbat and holidays. Religious clothing, such as the kippah head covering for men, are worn at all times by Orthodox Jews or during periods like prayer and religious study by many non-Orthodox Jews. Traditional Jewish kosher dietary laws determine what animals may be eaten (mammals with split hooves that chew their cud and sea animals with fins and scales), how foods may be eaten (dairy and meat may not be eaten together), and how animals may be slaughtered. Reform Judaism does not generally follow kosher rules. The relative roles of men and women in Jewish practices vary across denominations, with greater gender differentiation in Orthodox Judaism.