The third house accounts for our speech, writing, texts and emails, letters, relationships with our siblings, and our immediate neighborhood. It is ruled by Mercury and Gemini, so the location of the planet and any aspects to it will have an affect on this house.
The third house rules our hands, arms, shoulders, the nervous system, and the lungs. It is a cadent house, meaning any planet here will find it difficult to express itself through the native.
Planets that are found here will energize our speech and writings. The association with neighbors and family because the third house is still a personal house. Our communication is different with people in our neighborhood than with strangers in a foreign land or at college (which are related to the ninth house). Therefore, the third house is more in tune with the personality’s expression in familiar venues.
The sign on the third house cusp will describe how the native experiences communication with the world around him. An Aries third house is aggressive in speech and often finds himself arguing with siblings.