get- a bill of divorce that a husband gives a wife.
From the moment that the get reaches a woman's hands, she ceases to be her husband’s wife. In the words of the Torah, the get is a “writ of manumission”- sefer kritut. The get cancels the kinyan relationship that exists between husband and wife so long as they are married, and frees the women to marry another man (except a cohen). In the language of the Mishna: “a woman frees herself with the delivery of the get or with the death of her husband."
mamzer- a child born to a married woman who became pregnant from a man who is not her husband;
or a child born to parents of an incestuous relationship (sexual intercourse between blood relatives that is prohibited under Jewish law). A mamzer cannot “be part of the community.” A mamzer can only marry a convert or another mamzer. The child of a mamzer is a mamzer for generations.
agunah
is a woman whose husband has disappeared or does not have the capacity to deliver a bill of divorce to his wife because of his physical or mental condition. An agunah is trapped in a marriage that exists “on paper” alone, and she cannot free herself from this marriage or marry another man.
mesurevet-get (victim of get refusal)
is a woman who is in possession of a rabbinic court decision ordering her husband to give her a get, or who is in the middle of legal proceedings in which she seeks a get from her husband, and her husband refuses to deliver the get to her. The mesurevet get is not considered free to marry another man until her husband delivers a get to her.
Most modern writers conflate the terms agunah and mesurevet get.
kinyan be’kiddushin
This refers to the legal act that gives the husband exclusive conjugal rights to his bride. Upon the act of kinyan, the wife is forbidden to other men. The huband is not forbidden by this act to other women.
get meuseh (the forced divorce) - a bill of divorce that is not given of the free will of the husband.
The coerced divorce is invalid even if the coercion is done by rabbis, and even if the get has been authorized and conducted by the rabbinic courts. However, if the rabbinic courts issue a decision ordering, or better yet compelling, the husband to deliver a bill of divorce to his wife, the bill of divorce is valid (kosher) even if not given of the free will of the husband.



