Related על עדיות 8:2

The [legal] power of a wife is greater than the power of a yevamah (one whose husband died with no children and now is in a legal bond with her former brother-in-law which either ends in marriage or halitzah) [in some respects], and the power of a yevamah is greater than the power of a wife [in other respects]. The power of a wife is stronger—for a wife eats terumah [if her husband is a kohen] as soon as she enters the bridal chamber, even before she has had sex—which is not true for the yevamah. The power of the yevamah is stronger—for a man who has sex with his yevamah (i.e. his dead brother's wife), whether intentionally or unintentionally, whether forced or willingly, even if she is in her father's house, he acquires [her as a wife]—which is not true of a wife [with whom a man would need to have sex with the purpose of betrothal].