Yevamot (Hebrew: יבמות, "Brother's Widow", also pronounced Yevamos, or Yavmus) is a tractate of the Talmud that deals with, among other concepts, the laws of Yibbum (ייבום, loosely translated in English as levirate marriage), and, briefly, with conversion to Judaism.
Yevamot, along with Eruvin and Niddah, is considered one of the three most difficult tractates in the Babylonian Talmud.
A Hebrew mnemonic for the three is עני (ani, meaning "poverty").
[1] Yibbum is the Torah law (Deuteronomy 25:5–10) by which the brother of a man who died without children is allowed and expected to marry the widow.
In any case where Yibbum applies, Halitsah may be performed as an alternative.