The third house represents understanding through information, and what we know as a result of interactions within our community. "Community" here means neighbors, siblings, short journeys, letters, news and rumors. This house rules our rational thought and conscious mind, memory, speech, early education and environment, writing and communication, dexterity and taken-for-granted skills, explorations, investigations, inquiry, and research of all kinds. Planets in the third house describe the quality and quantity of our mental and nervous energy.

Geometrically speaking, the third house is that one-twelfth sector of the local sky clockwise from the nadir (see above picture), and is occupied by planets in the two hours after they pass through the lowest point of the local sky.

With the Sun in the third house you're a thinking person, and your sense of purpose and your will are focused in communication, ideas, and your immediate environment/neighborhood. You can get your ideas across well to others, and would make a good teacher, writer or lecturer. You're naturally curious, so study, research, and investigations of all kinds appeal to you. You have a good relationship with your brothers or sisters, and your early years were probably pleasant ones.

Famous people born about the same time of day as you (Sun in the third house) are/were Louisa May Alcott, Hans Christian Anderson, Lauren Bacall, Philip Berigan, Jeff Bridges, Pat Buchanan, Pearl Buck, Paul Cezanne, Sir Winston Churchill, Buster Crabbe, Geena Davis, Christian Dior, Walt Disney, Britt Ekland, Lou Ferrigno, Redd Foxx, A. J. Foyt, Buckminister Fuller, Alberto Giacometti, Terry Gilliam, Cary Grant, Merle Haggard, Jim Henson, Mick Jagger, Gary Kasparov, Stephen King, Charles Lindburgh, Dean Martin, Roger Moore, James Olmos, Jack Paar, Louis Pasteur, Luciano Pavarotti, Jean Piaget, Lily Pons, Vinncent Price, Giacomo Puccini, Carlos Santana, George Seurat, Tony Shalhoub, Beverly Sills, Britney Spears, Sting, Jimmy Swaggart, Lily Tomlin, Rip Torn, Lili Tomlin, Denzel Washington, Hank Williams, Woodrow Wilson, Shelley Winters and Tammy Wynette.

If the Sun is within 12° of the nadir (the fourth house cusp), then it is conjunct the fourth house cusp and much of the foregoing interpretation starts to become weaker. If the Sun is in the third house AND within 4° or 5° of the nadir, then it is said to be on the "dark side" of the fourth house, and it influence will be felt in the fourth as well as in the third house. The closer a third house Sun is to the nadir, the more it will be interpreted as though it were in the fourth house; when less than 3° from the nadir, a third house Sun expresses itself primarily—and eventually entirely—in the fourth house.