Sun sign traits: what a sun sign actually describes
A sun sign records one thing: which twelfth of the year a birth fell into. It is the sun's ecliptic longitude at that moment, measured from the equinox and divided by 30°, a position on a seasonal scale rather than a patch of stars. The twelve familiar descriptions are not twelve kinds of person either. They are four elements crossed with three modalities: six words rearranged.
The zero point is the equinox, not a constellation
The sun completes one circuit of the ecliptic in a year, and where that circle is measured from settles everything after it. Western astrology begins not at a star but at the vernal equinox, the direction of the sun at the instant it crosses the celestial equator going north. That point is 0° Aries, and the other eleven signs follow at intervals of 30°.
So 0° Cancer is the June solstice, 0° Libra the September equinox, 0° Capricorn the December solstice. The twelve signs are twelfths of the solar year rather than districts of the star map, and to be born under Aries is to be born in the first month after spring begins in the northern hemisphere.
The equinox point itself drifts. Precession carries it backwards about one degree every seventy-two years, and it now stands some 24° from the constellations the signs were named after, nearly a whole sign. The recurring story about a thirteenth sign, Ophiuchus, is a collision between two frames: Western astrology keeps the seasonal one, Indian astrology the stellar one, and each is consistent inside itself.
Four elements by three modalities
Twelve is not twelve kinds. It is four by three. The elements, fire and earth and air and water, repeat every fourth sign around the ecliptic; the modalities, cardinal and fixed and mutable, repeat every third. Four and three share no factor, so a single circuit produces each of the twelve pairings exactly once and then closes.
The modalities are defined by position within a season. The cardinal signs, Aries and Cancer and Libra and Capricorn, begin at the equinoxes and the solstices, on the hinge where one season turns into the next. The fixed signs, Taurus and Leo and Scorpio and Aquarius, hold the middle of each season, the stretch that changes least. The mutable signs, Gemini and Virgo and Sagittarius and Pisces, sit at the end, where a season is already dissolving into the one behind it. Initiating, sustaining and adapting describe the calendar before they describe anybody.
In order: Aries fire cardinal, Taurus earth fixed, Gemini air mutable, Cancer water cardinal, Leo fire fixed, Virgo earth mutable, Libra air cardinal, Scorpio water fixed, Sagittarius fire mutable, Capricorn earth cardinal, Aquarius air fixed, Pisces water mutable. A third term, the ruling planet, belongs to the same bundle; this site computes the sun, the moon and the ascendant and nothing else, so it writes nothing about it.
Six terms, twelve paragraphs
Most of what circulates as twelve-sign personality writing is the table above translated into character words: fire as speed, earth as texture, air as distance, water as saturation; cardinal as beginning, fixed as holding, mutable as adapting. Six terms will generate twelve paragraphs, and the twelve will share a skeleton. Set side by side, they read less like twelve observations than like one grid described twelve times.
The second reason such writing reads generically is arithmetic. A sun sign covers about a twelfth of everyone alive, some seven hundred million people, and a sentence that must hold for seven hundred million people can only be built out of sentences that are easy to satisfy.
Such descriptions also pair a quality with its shadow, decisive and impatient, steady and immovable, so that either behaviour confirms the reading. That is not a defect in the arithmetic. It is a property of an inherited vocabulary that was never built to be refuted.
A northern calendar, read as a character
The whole scheme describes the northern year. An Aries birthday in Buenos Aires or Auckland falls in early autumn, and no branch of Western astrology reverses the signs to suit it. Whatever the twelve descriptions are, they are not descriptions of the weather anyone was actually born into.
The tradition also reads the sun as a direction rather than a starting condition, a distinction /blog/three-placements draws across all three placements. The implication is rarely spelled out: a direction becomes visible only once some distance has been covered, which is why the description is usually said to fit better later than earlier.
The weakness of that argument deserves naming as well. Wait and it will fit is an excuse available for any mismatch, and this site cannot refute it. Astrology is offered here as a frame for reflection rather than a forecast of fact, and the line does not move at the moment moving it would be convenient.
What to read when it does not fit
Doubt the date first. Sign boundaries fall at a different hour each year, and seventeen calendar dates change sign somewhere between 1930 and 2030; they are listed at /zodiac-dates and the drift behind them is worked out at /blog/zodiac-dates-shift. Then look past the sun altogether, since the moon and the ascendant are fixed by different motions and are free at /moon-sign and /rising-sign.
Last, a daily horoscope is not a character sketch. /daily is written against the moon phase of that day, which belongs to everyone standing in it, and asks what the day is like rather than what a person is like.