Marriage matching or match making is a solemn decision taken on behalf of the boy and a girl before they tie the knot to hold and to behold each other for the rest of their lives. The Hindus ensure that the compatibility of this solemn lifelong binding enables the couple to live 'happily ever after'.
For this vital decision of their lives, the parents of both the girl and the boy who are to get married and the elders of their families get together; they then follow an ancient method, laid down by the sages of old, to see the marriage compatibility between the girl and the boy. This method is called 'porutham' or koota agreement.
Poruthams are chalked out after the study of the birth stars of both the boy and the girl who are contemplating marriage. The sages had initially devised 20 poruthams but now only 10 are in use. According to them, there are 27 birth stars (nakshatras) for each person in an oval configuration which constitutes a zodiac. The zodiac influences the person through the nine planets (navgrahas).
The ten poruthams (kootas) thus chalked out are: dinam, ganam, yoni, rasi, rasiyathipaty, rajju, vedha, vasya, mahendram and stree deergham. Yoni Porutham is important because this is the porutham which helps in determining the sexual compatibility between the couple after marriage and forms the basis of the marriage as this is the sole aim in a man and a woman coming together while living together in harmony is secondary.
Yoni porutham should be mapped out for both the girl and the boy and not just for the girl because it is accountable for the physical compatibility of the married couple. There is no fixed parameter which says that a particular zodiac star is compatible physically with the other's star (nakshatra). Yoni porutham can only say about the incompatibility of the stars in question, not about their compatibility as is evident in daily life where the husband and the wife are not always at the same emotional and physical relationship with one another; on one occasion they may be compatible but on other occasion they may not be. Therefore, it is an assumption that if one nakshatra is incompatible, the other nakshatra may or may not be compatible.
Some married couples are found never to be at a satisfactory compatibility with each other, either physically or emotionally. The yoni porutham is applicable for such relationships. Here, the human behaviour during sexual relations is taken into consideration and accordingly the incompatibility is charted which when looked at conversely, shows what is compatible. To begin with, the 27 birth stars are made into groups. The yoni porutham is tabulated by appointing one animal force to each such group e.g. if the boy's nakshtra comes under a 'cat' and the girl's comes under 'rat' then the yoni porutham of the couple is incompatible since the rat and the cat are enemies and so there is no possibility of the two living in compatible physical and emotional relationship together.