Polygyny is having more than one wife. Polygamy is the term used for mulitple spouses either male or femle and Polandry is having more than one husband. In Islam, Polygyny is allowed but the man is only allowed to have up to four wives. There are strict rules governing the taking of more than one wife.
Of course most of the world would look at this and think terrible thoughts. The ideal case is the opposite.
First, it allows more women who wish to be married the opportunity. Secondly, it allows for morality in the society. If a man has more than one wife he may not have the energy to wander. Third, if the women can get along, it can ease the burden of child care and house work. Fourth and here I will relate a story that was told at a meeting I attended on Women in Islam several years ago.
A man had four wives and they were going to do some things together for fun. The situation arose where it was one the wives turn to stay with the husband. The difference of opinion was on who was going to have to stay with the husband while the other three had fun.
The point is that it can relieve one woman from having to constantly see to her husbands needs. The second is as in the story, can you imagine what it does for a man's ego when his wives have to figure out who has to stay with him, kind of the shoe being on the other foot. Allah (SWT) is just.
Polygamy is allowed but it must meet certain conditions and these conditions are strict enough that if the Qur'an and Sunnah are followed the women will receive fair treatment. I wish to point out that ideal and actual are not the same. It is a decision that must be entered into with great care and if the first wife feels she can not abide with another wife she can ask for a divorce.
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