Third house of the horoscope is known as Bandhu Bhava in Vedic Astrology which literally means House of Brothers. Hence the third house mainly signifies relations with brothers, friends, colleagues and neighbors. This house is of great importance when predicting about gains and losses once faces while dealing with brothers, friends and colleagues. A strong third house would usually indicate a successful person who has got the support of his brothers, friends and colleagues. Such people have very dedicated friends and brothers who are willing to do anything to make these persons grow in life. On the other hand, a horoscope where the third house is under the bad influence of negative planets due to placement or aspect would usually indicate a person who faces major financial losses and other kinds of setbacks due to his friends and brothers working against him. Such people usually have friends who betray them and bring losses and setbacks to them. Their friends and colleagues are usually the ones who bring them down by backbiting and speaking ill of them behind their back.
This house represents shoulders and arms among the body parts and right arm and right shoulder in particular. It also represents nervous system and respiratory system in a horoscope. Bad influences on this house can lead to disease including respiration like Asthma, problems related to nervous system and paralysis etc. among other diseases.
This house also indicates the strength and courage a person may have and his initiative and progress in the field of sports and other professions involving hard and skilled physical activities. It also represents the power to understand things, writing skills and communication skills in particular. People with a strong third house are usually blessed with very good communication skills and know how to make other people come round to their point of view. Such people are usually very successful in the fields requiring communication skills. On the other hand a weak or badly influenced third house would make a person have little or no communication skills and such people are usually not successful with any fields requiring communications and so they usually work at back ends which require least communication skills.