Astrology Glossary

The building blocks of every birth chart, in plain English. Look up an aspect like the trine or square, get to know the four elements and three modalities, or find your decan, the 10° slice of your sign that adds a second flavor to who you are.

Aspects

The angles between planets — how two parts of a chart talk to each other.

Conjunction0°Trine120°Square90°Opposition180°Sextile60°

Elements

Fire, earth, air, and water — the four temperaments that group the signs.

Fire SignsAries · Leo · SagittariusEarth SignsTaurus · Virgo · CapricornAir SignsGemini · Libra · AquariusWater SignsCancer · Scorpio · Pisces

Modalities

Cardinal, fixed, and mutable — how each sign starts, holds, or releases.

Cardinal SignsAries · Cancer · Libra · CapricornFixed SignsTaurus · Leo · Scorpio · AquariusMutable SignsGemini · Virgo · Sagittarius · Pisces

Decans

Each sign split into three 10° thirds, each with its own sub-ruler and flavor.

Aries First DecanMar 21 – Mar 30Aries Second DecanMar 31 – Apr 9Aries Third DecanApr 10 – Apr 19Leo First DecanJul 23 – Aug 1Leo Second DecanAug 2 – Aug 11Leo Third DecanAug 12 – Aug 22Sagittarius First DecanNov 22 – Dec 1Sagittarius Second DecanDec 2 – Dec 11Sagittarius Third DecanDec 12 – Dec 21Taurus First DecanApr 20 – Apr 29Taurus Second DecanApr 30 – May 10Taurus Third DecanMay 11 – May 20Virgo First DecanAug 23 – Sep 1Virgo Second DecanSep 2 – Sep 11Virgo Third DecanSep 12 – Sep 22Capricorn First DecanDec 22 – Dec 31Capricorn Second DecanJan 1 – Jan 10Capricorn Third DecanJan 11 – Jan 19Gemini First DecanMay 21 – May 31Gemini Second DecanJun 1 – Jun 10Gemini Third DecanJun 11 – Jun 20Libra First DecanSep 23 – Oct 2Libra Second DecanOct 3 – Oct 12Libra Third DecanOct 13 – Oct 22Aquarius First DecanJan 20 – Jan 29Aquarius Second DecanJan 30 – Feb 8Aquarius Third DecanFeb 9 – Feb 18Cancer First DecanJun 21 – Jul 1Cancer Second DecanJul 2 – Jul 12Cancer Third DecanJul 13 – Jul 22Scorpio First DecanOct 23 – Nov 1Scorpio Second DecanNov 2 – Nov 11Scorpio Third DecanNov 12 – Nov 21Pisces First DecanFeb 19 – Feb 29Pisces Second DecanMar 1 – Mar 10Pisces Third DecanMar 11 – Mar 20

These terms knit the whole sky together. Read your zodiac sign, explore the planets in the signs, learn the twelve houses, or start from the beginning in our guide to astrology.

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Frequently asked questions about astrology terms

What is an aspect in astrology?
An aspect is the angular relationship between two planets as seen from Earth. Common aspects include the conjunction (0°, planets in the same place), the trine (120°, considered harmonious), and the square (90°, considered challenging). Each aspect describes how two planetary energies interact in a chart.
What are the four elements in astrology?
The four elements are Fire (Aries, Leo, Sagittarius), Earth (Taurus, Virgo, Capricorn), Air (Gemini, Libra, Aquarius), and Water (Cancer, Scorpio, Pisces). They group signs by temperament: Fire = initiating, Earth = grounding, Air = communicating, Water = feeling.
What are the three modalities?
The modalities (Cardinal, Fixed, and Mutable) describe how each sign approaches action. Cardinal signs (Aries, Cancer, Libra, Capricorn) initiate; Fixed signs (Taurus, Leo, Scorpio, Aquarius) sustain; Mutable signs (Gemini, Virgo, Sagittarius, Pisces) adapt.
What is a decan?
Each zodiac sign spans 30 degrees of the ecliptic, and a decan is one of three 10-degree slices of that range. Your decan adds a secondary planetary ruler and a secondary flavor to your sun sign, for example, a Scorpio born in the first decan has a different nuance than one born in the third.
How do aspects, elements, and modalities relate to a birth chart?
A birth chart plots every planet's position by sign and degree. The sign tells you which element and modality a planet operates in; the aspects tell you which planets are in dialogue with each other. Together they form the grammar that astrologers use to describe a person's tendencies and timing.
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