Erusin as used in Torah language (such as Devarim 22:23) is when Kidushin has been done. She is forbidden to other men. Get or death detaches her from her husband, just like after the final stage of Nisu'in.

However, nowadays the word Erusin is commonly used for the stage of agreeing to get married (engagement). No divorce is needed or is possible then.

See Background to the Daf included below.

All the best,

Reuven Weiner

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(a) SHIDUCHIN - In anticipation of the marriage, the man may formally agree to marry the woman. This is known as "Shiduchei" (Kidushin 12b). None of the Halachos of marriage apply to them at this point, although they may obligate themselves to each other monetarily to guarantee that the marriage takes place (see Tosfos 8b end of DH Manih). Also, the families of the bride and the groom may promise the young couple specified sums, upon the realization of the marriage (see Kidushin 9b and Tosfos). These written agreements are also known as "Shetarei Pesikta" (ibid.) or, nowadays, "Tena'im."

(b) KIDUSHIN - The actual marriage begins when the man gives the woman Kesef (money or any object or favor which is of value to the woman), Shtar (a marriage document) or Bi'ah in order to effect Kidushin. This stage, known as "Eirusin" in the Torah (Devarim 22:23), was given the name "Kidushin" by the Rabanan to denote that through this act, the husband prohibits the wife to the entire world, just as Hekdesh (a sanctified object) is prohibited for ordinary use (Kidushin 2b; see also Tosfos 7a DH v'Nifshetu). A single Berachah, Birkas Eirusin, is made at the time of Eirusin (Kesuvos 7b).

(c) NISU'IN - The Nisu'in, or completion of the marriage, is accomplished through Chupah. The Rishonim offers various definitions for Chupah (see Insights to Kesuvos 57:1), but in general it means that the husband brings his wife into his house. Seven Berachos are recited, and these Berachos are repeated during all meals made in honor of the new couple, for seven days. (There are numerous conditions under which the seven Berachos are not recited, or are recited for fewer days, see Kesuvos 7a, 8a.) At this stage, the mutual obligations of Ishus and the Kinyan Mamon take effect.