There is a clear distinction between a forced marriage and an arranged marriage.
In arranged marriages, the families of both spouses take a leading role in arranging the marriage but the choice whether or not to accept the arrangement remains with the prospective spouses.
In forced marriage, one or both spouses do not (or, in the case of some adults with disabilities, cannot) consent to the marriage and duress is involved. "Duress" can include physical, psychological, sexual, financial and emotional pressure.
Parents who force their children to marry often justify their behaviour as protecting their children, building stronger families and preserving cultural or religious traditions. They often do not see anything wrong in their actions. Forced marriage cannot be justified on religious grounds; every major faith condemns it and freely given consent to a marriage is a prerequisite of all religions.