A woman's prescribed waiting period after divorce or death of husband. It is 4 months and 10 days.
If there was no period of iddah and the woman married another man and discovered she was pregnant then she would be unable to tell who the father of the child was. Iddah solves this potential problem. Iddah also applies in the situation where a woman converts while she is married to a none-Muslim husband, she has 4 months and 10 days for him to accept Islam or else the marriage dissolves.