Sun Sign: the constellation that the sun was in during one's birth.
The sign of the zodiac that a person is born under.
The sign in which the Sun was in at the time of birth. Long over-emphasized, which lead to the misconception that Sun Sign astrology was the sum total of astrology. For the Sun is only one of ten planets in the horoscope or birth chart. It is considered to be the true, inner personality of the individual. The Sun sign, Moon sign and ascendant are the three most important elements in a birth chart to understand the inner person (Sun sign), the outer person (ascendant) and the emotional expression (Moon sign) of the individual.
What people think of as their 'Sign' or 'Star Sign.' It is the position of the Sun in the Zodiac at the moment of one's birth. The Sign placement of the Sun shows an individual's basic character. It is the core of one's potential and uniqueness as an individual.