In astrology, the 7th house (opposite the 1st house) in your natal chart represents everything and everyone that is outside of yourself.
It's a cardinal air house denoting that it's about (superficial) encounters, meetings and interaction with the outer world (at large), with the public, an audience etc.
Because of the air element, it's about communication, exchange of thoughts and ideas and all kinds of interactions.
Because it's a cardinal house, it's also about (im)pulses and initiating urges.
It's above all about our "social urges" and the need to "connect."
In the 7th house, we find the impulse to meet and encounter the outer world. The 7th house is about socializing, about the people we live with, the "others" we meet (clients, customers, vendors, people in the street,...).
Because of the polarity with the 1st house (representing your own self), it also relates to what attracts you or whom you are attracted to.
It's also about your "significant other" as a person and being.
It's not really about marriages.
In our opinion, marriage is part of the whole 3rd Quadrant (houses 7, 8 and 9). Why? Because:
in the 7th house, you just meet/encounter the other (the cardinal principle).
in the 8th house you bond with the other (it's a fixed water house, representing emotional connections and bonds) (the fixed principle).
in the 9th house you make the bond and "the other" public (mutable houses spread and become visible) (the mutable principle).
The zodiac sign(s) on the cusp and in the 7th house describe these other people and situations you are attracted to. The planets in the 7th house, which we want to delineate now, reveal yet more about the other(s).
We only list the planets separately. In case two or more planets reside in the 7th house, the meaning can alter substantially (in our opinion, you CANNOT blend the meaning of the individual delineations as such -- the outcome seems to be more than the sum of the parts).
It seems that stelliums or multiple conjunctions in the 7th house have their own meaning which still needs further research!
And now to the delineations of the planets in the 7th house...
The Sun in the 7th House
The Sun represents your ego and physical body. You want that the outer world sees you physically.
you want to get noticed physically
other persons (or your significant other) are related to mile stones in your life that raise creativity and more self-expression.
you tend to attract (male) persons of authority
relationships become a focal point in life
The Moon in the 7th House
you crave meetings and encounters
you are attracted to sensitive people who, quite often, love children
there is no real stability in meeting people (people come and go) but encounters are quite cyclic (you meet the same person again after some time, often following a certain cycle).
you tend to attract moody people
you may be attracted to children and/or childish people
you tend to talk to your partner as if you talk to a child (childish, with diminutives and often degrading the other)
there is some calculation in everything you do
Mercury in the 7th House
you need a public to talk to, to communicate with
you need a mental and intellectual relationship
you are attracted to (much) younger people and/or slim people
you love poetry, writings etc...
relationships tend to be full of opportunism and are often a calculated act
you need aesthetically pleasing people full of charm
you cannot live without people in your environment
you tend to be attracted to rather passive (lazy?) people who cannot stand a fight or argument
you love multi-tasking because it makes you feel less lonely
because Venus cannot stand arguments, chances are that differences in this relationship are not spoken out, resulting in miscommunication and dissatisfaction in the long run