Erusin (Hebrew: אירוסין, romanized: ʾerusin, also Babylonian ʾirrusin[1]) is the Hebrew term for betrothal. In Modern Hebrew, erusin means engagement, but this is not the historical meaning of the term, which is the first part of marriage, the second part being the nissuin "nuptials".[2]
Since the Middle Ages[3] it is customary for the marriage to occur immediately after the betrothal, and to perform the betrothal during the marriage ceremony itself. Previously, this was not the case, and there were often several months between the two events, according to Ketubot 57b: "a virgin is given twelve months to prepare for her wedding? ... a widow given her thirty days".
In Hebrew and rabbinic literature, betrothal is frequently referred to as "sanctification" (Hebrew: קידושין, romanized: qiddushin), on account of the bride becoming "sanctified" (dedicated) to the groom.