Sagittarius is the ninth astrological sign

Astrological sign

Astrological signs represent twelve equal segments or divisions of the zodiac. According to astrology, celestial phenomena reflect or govern human activity on the principle of "as above, so below", so that the twelve signs are held to represent twelve basic personality types or characteristic modes...

 in the Zodiac

Zodiac

In astronomy, the zodiac is a circle of twelve 30° divisions of celestial longitude which are centred upon the ecliptic: the apparent path of the Sun across the celestial sphere over the course of the year...

, which spans the zodiac between the 240th and 269th degree of celestial longitude. According to the tropical zodiac of western astrology, the Sun

Sun (astrology)

The sun is considered a very important part of astrology. It, as well as the Moon, are the most important of the astrological planets, and the two of them are often referred to as the luminaries. In Greek mythology the sun was represented by Apollo, the god of light, and Helios, the god of the sun...

 transits this area of the zodiac between November 22 and December 21 each year (sometimes the dates vary slightly).
Sagittarius is seasonally associated with the transition from autumnal moisture to mid-winter dryness.