Yevamot is the first tractate in the order of Nashim. Admittedly, some commentaries place Yevamot after Gittin (Meiri), but this is not widely accepted. While the tractate focuses mainly on the halakhot of levirate marriage, the elucidation of these halakhot necessitates an in-depth clarification of the halakhot of marriage in general. These include forbidden and disqualified marriages, i.e., those women with whom relations are forbidden with a certain man, whether by Torah law or by rabbinic law, as well as the definition and severity of these prohibitions. Consequently, the comprehensive discussions of tractate Yevamot form the basis of the entire order of Nashim.