The seventh house is the 7th from ascendant when counted anti-clockwise. If the master of 7th house is present in exaltation or in own house, specially if in center (1,4,7,10) or in trine (1,5,9), it will give native good results. The 7th house is also called the Kalatra Sthan (the house of your wife/spouse/relationships). This house is of utmost importance since it represents one of the most important aspects of one's life. One's life partner is someone with whom you share a lot of things, and some of them you don't share with anyone else in this world. So, it is very necessary that the lord of 7th house is in good position and it must be taken into consideration only 2nd to 1st house. One must definitely work towards strengthening the lord of 7th house.
The 7th house mostly signifies the following:
1. Your life partner/spouse etc.
2. Your relationships in general
3. Partnerships and Business (people other than the native and native's relationship with them)
4. Friends and specifically the world in which you move around
5. Large intestine, rectum, uterus, ovaries and testes
6. Prostate gland, seminal vesicle, urethra, anal canal, and semen
7. Sexual union
8. Influence, success and reputation in foreign travels.
It is through the 7th house that the native perceives other people. During the dasa, antardasa of the Lord of 7th house, you will see the above significations of 7th house, taking prominence in your life. The number of planets present in 7th house can actually indicate the number of people with whom you can have a 'serious' relationship. The prediction of marriage/serious relationship can also be done by looking at the master of 7th house, its dasa, antardasa or any planet affecting it or 7th house. The same is valid for transits too. The relationships are also considered via the divisional chart D9. The 7th house in D9 will indicate the nature of your partner. It will also indicate the stability of your relationship.