Reference

Glossary

122 terms, in plain words. Every term the lessons and the chart pages use, with anchors you can link to.

Filter the glossary

122 terms.

The sky

What is actually up there, and how it is measured.

Celestial equator: Earth's equator projected onto the sky. It crosses the ecliptic at the two equinoxes.
Degree and arcminute: A degree (°) is one 360th of a circle and an arcminute (′) is one 60th of a degree. A position inside a sign runs from 0°00′ to 29°59′.Also: arcminute
Ecliptic: The path the Sun appears to follow against the background stars over a year. The Moon and the planets stay close to it, which is why they all travel through the same twelve signs.
Ecliptic longitude: A position along the ecliptic, measured in degrees from 0° to 360°. Every body in a chart has one; the sign and the degree within the sign are read from it.Also: longitude
Ephemeris: A table of computed positions of the Sun, Moon and planets over time. Genastro computes charts from the Swiss Ephemeris, and you can check any position against another ephemeris.
Equinox: One of the two moments each year when the Sun crosses the celestial equator and day and night are nearly equal. The March equinox is where the tropical zodiac puts 0° Aries.
Horizon: The line where the sky meets the ground at the birth place. Whatever was above it was visible; whatever was below it was not.
Meridian: The imaginary line from due north through the point straight overhead to due south. The Sun crosses it at local solar noon.
Precession: The slow wobble of Earth's axis, one full cycle in about 26,000 years. It moves the equinoxes backward against the stars, which is why the tropical and sidereal zodiacs drift apart.
Solstice: One of the two moments each year when the Sun is farthest north or south of the celestial equator. The tropical zodiac puts 0° Cancer at the June solstice and 0° Capricorn at the December one.
Zodiac: The band of sky centered on the ecliptic, divided in astrology into twelve signs of 30° each. Which way the band is anchored is the difference between the tropical and sidereal zodiacs.

Time and place

Clocks, zones and the instant of birth.

Daylight saving time: A seasonal shift of the clock, usually one hour. The engine records whether a birth fell inside one and corrects for it.Also: DST
Julian Day: A continuous count of days that names an instant without calendars or time zones. It is shown in the chart's instrument strip so the instant can be checked against any other tool.
Unknown birth time: When no birth time is given the engine computes the chart for local noon. The Sun's sign is almost always right, but the Ascendant, Midheaven, houses and sometimes the Moon's sign are not, so they are hidden.Also: noon chart
UTC: Coordinated Universal Time, the world's reference clock. Every local time is UTC plus or minus an offset, and the engine converts the birth time to UTC before it computes anything.Also: UT
UTC offset: How far a place's clock stood from UTC at a given date, such as UTC+1 for Lisbon in March 1994. Offsets have changed over the years, so the engine uses the one the place really had at the birth moment.Also: time zone

Reading a chart

The parts of a chart and the words for them.

Ascendant: The zodiac sign and degree on the eastern horizon at the moment of birth. It changes about every two hours and depends on the birth place, so it needs a birth time.Also: rising sign, ASC, rising
Big Three: The Sun sign, the Moon sign and the Ascendant sign taken together. They are the three placements that cover the most of a chart at a glance, and the combination is what the rarity checker measures.Also: Big Three
Birth chart: A map of where the Sun, Moon and planets were in the sky at one moment, seen from one place. It is computed from the birth date, time and place, and is also called a natal chart.Also: natal chart
Chart wheel: The circular diagram of a chart: the zodiac ring on the outside, the houses inside it, the bodies placed at their longitudes and lines drawn between bodies that make aspects.
Decan: A third of a sign: 10° of ecliptic longitude. Each sign has three, and traditions assign each one a ruler by different schemes.
Descendant: The point on the western horizon at birth, exactly opposite the Ascendant. It is the cusp of the 7th house.Also: DSC
Generic reading: A plain description of a placement that is the same for everyone who has it. Genastro labels these so they are not mistaken for a prediction or a statement about one person.
Imum Coeli: The point of the ecliptic directly opposite the Midheaven, at the bottom of the chart. It is the cusp of the 4th house in most house systems.Also: IC
Midheaven: The point where the ecliptic crossed the meridian above the horizon at birth. It is the top of the chart and the cusp of the 10th house in most house systems.Also: MC, medium coeli
Moon sign: The sign the Moon was in at birth. The Moon crosses a sign about every 2.3 days, so the date and, near a boundary, the time both matter.
Placement: One body at one position: its sign and degree, and with a known birth time its house. "Moon in Aries" is a placement.
Polarity: Fire and air signs are called positive (or yang) and earth and water signs negative (or yin) in traditional and modern astrology. The terms describe a grouping, not a judgment.
Ruler: The planet a tradition assigns to a sign as its home. Traditions differ: for Scorpio, traditional astrology names Mars and modern astrology names Pluto.Also: rulership
Sun sign: The sign the Sun was in at birth. It is set by the date alone and is the sign most people mean when they name "their sign".Also: star sign
The four angles: The Ascendant, Descendant, Midheaven and Imum Coeli: the four points where the ecliptic meets the horizon and the meridian. The houses are built around them.Also: angle
Tradition: A school of astrology with its own rules and vocabulary. Genastro attributes every interpretive statement to one, and never presents a reading as a plain fact.
Transit: The current position of a body compared with a chart. The learn lessons do not use transits, and Genastro publishes no daily horoscopes.

Signs, elements and modalities

The twelve signs and the groups they fall into.

Ayanamsa: The angle between the tropical and sidereal zodiacs at a given date. Genastro uses the Lahiri ayanamsa, which is about 23°47′ for a birth in 1994.
Element: The grouping of the twelve signs into fire, earth, air and water, three signs each. Signs of one element sit four signs apart, 120° from each other.
Modality: The grouping of the twelve signs into cardinal, fixed and mutable, four signs each. It follows each sign's place in its season.Also: quality
Sidereal zodiac: A zodiac anchored to the stars. It is the tropical zodiac shifted by the ayanamsa, so most placements land one sign earlier. Vedic astrology uses it.Also: sidereal
Sign: One of twelve equal 30° divisions of the zodiac, starting with Aries at 0°. A body's sign is read from its ecliptic longitude.
Tropical zodiac: A zodiac anchored to the seasons: 0° Aries is where the Sun is at the March equinox. Its signs are 30° divisions of the year, not the constellations of the same names.Also: tropical
Aries: Aries covers 0°–30° of the tropical zodiac and is a cardinal fire sign. Traditional and modern astrology both name Mars as its ruler. The Sun is typically in it from 21 March to 19 April, give or take a day by year.
Taurus: Taurus covers 30°–60° of the tropical zodiac and is a fixed earth sign. Traditional and modern astrology both name Venus as its ruler. The Sun is typically in it from 20 April to 20 May, give or take a day by year.
Gemini: Gemini covers 60°–90° of the tropical zodiac and is a mutable air sign. Traditional and modern astrology both name Mercury as its ruler. The Sun is typically in it from 21 May to 20 June, give or take a day by year.
Cancer: Cancer covers 90°–120° of the tropical zodiac and is a cardinal water sign. Traditional and modern astrology both name the Moon as its ruler. The Sun is typically in it from 21 June to 22 July, give or take a day by year.
Leo: Leo covers 120°–150° of the tropical zodiac and is a fixed fire sign. Traditional and modern astrology both name the Sun as its ruler. The Sun is typically in it from 23 July to 22 August, give or take a day by year.
Virgo: Virgo covers 150°–180° of the tropical zodiac and is a mutable earth sign. Traditional and modern astrology both name Mercury as its ruler. The Sun is typically in it from 23 August to 22 September, give or take a day by year.
Libra: Libra covers 180°–210° of the tropical zodiac and is a cardinal air sign. Traditional and modern astrology both name Venus as its ruler. The Sun is typically in it from 23 September to 22 October, give or take a day by year.
Scorpio: Scorpio covers 210°–240° of the tropical zodiac and is a fixed water sign. Traditional astrology names Mars as its ruler; modern astrology names Pluto. The Sun is typically in it from 23 October to 21 November, give or take a day by year.
Sagittarius: Sagittarius covers 240°–270° of the tropical zodiac and is a mutable fire sign. Traditional and modern astrology both name Jupiter as its ruler. The Sun is typically in it from 22 November to 21 December, give or take a day by year.
Capricorn: Capricorn covers 270°–300° of the tropical zodiac and is a cardinal earth sign. Traditional and modern astrology both name Saturn as its ruler. The Sun is typically in it from 22 December to 19 January, give or take a day by year.
Aquarius: Aquarius covers 300°–330° of the tropical zodiac and is a fixed air sign. Traditional astrology names Saturn as its ruler; modern astrology names Uranus. The Sun is typically in it from 20 January to 18 February, give or take a day by year.
Pisces: Pisces covers 330°–360° of the tropical zodiac and is a mutable water sign. Traditional astrology names Jupiter as its ruler; modern astrology names Neptune. The Sun is typically in it from 19 February to 20 March, give or take a day by year.
Fire: Fire is the element of Aries, Leo and Sagittarius. Classical authors described it as hot and dry; modern psychological astrology associates it with spirit, enthusiasm and action.
Earth: Earth is the element of Taurus, Virgo and Capricorn. Classical authors described it as cold and dry; modern psychological astrology associates it with matter, practicality and endurance.
Air: Air is the element of Gemini, Libra and Aquarius. Classical authors described it as hot and moist; modern psychological astrology associates it with intellect, connection and ideas.
Water: Water is the element of Cancer, Scorpio and Pisces. Classical authors described it as cold and moist; modern psychological astrology associates it with feeling, intuition and empathy.
Cardinal: Cardinal signs are Aries, Cancer, Libra and Capricorn. They open a season: each begins at an equinox or a solstice. Modern astrology associates them with initiating, leading and beginnings.
Fixed: Fixed signs are Taurus, Leo, Scorpio and Aquarius. They sit in the middle of a season. Modern astrology associates them with sustaining, focus and persistence.
Mutable: Mutable signs are Gemini, Virgo, Sagittarius and Pisces. They close a season, right before the next one begins. Modern astrology associates them with adapting, transition and flexibility.

Bodies

The Sun, Moon, planets and calculated points a chart plots.

Body: Anything a chart plots: the Sun, the Moon, the eight other planets, Chiron and two calculated points. Genastro plots thirteen.
Ingress: The moment a body enters a new sign. Genastro's ingress dates come from the computed positions, so you can check them.
Luminary: The Sun or the Moon, the two lights. Astrologers call them planets as well, although astronomers do not.Also: luminaries
Planet: In astrology, the Sun and Moon plus Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. The traditions of the ancient world knew only the first seven.Also: planets
Retrograde: A planet is retrograde when it appears to move backward against the stars as seen from Earth. It is an optical effect: Earth overtakes the planet on its orbit, and the planet does not reverse.Also: Rx
Station: The days when a planet appears to stop against the stars before it turns retrograde or direct again.
Sun: The Sun is a luminary in the chart. It appears to travel once around the zodiac in a year. Its traditional domicile is Leo. Modern astrology associates it with identity, vitality and purpose.
Moon: The Moon is a luminary in the chart. It circles the zodiac in about 27.3 days. Its traditional domicile is Cancer. Modern astrology associates it with emotion, instinct and habit.
Mercury: Mercury is a planet in the chart. It takes about 88 days to orbit the Sun. Its traditional domicile is Gemini and Virgo. Modern astrology associates it with mind, communication and analysis.
Venus: Venus is a planet in the chart. It takes about 225 days to orbit the Sun. Its traditional domicile is Taurus and Libra. Modern astrology associates it with love, values and harmony.
Mars: Mars is a planet in the chart. It takes about 687 days to orbit the Sun. Its traditional domicile is Aries and Scorpio. Modern astrology associates it with drive, assertion and desire.
Jupiter: Jupiter is a planet in the chart. It takes about 12 years to orbit the Sun. Its traditional domicile is Sagittarius and Pisces. Modern astrology associates it with growth, meaning and abundance.
Saturn: Saturn is a planet in the chart. It takes about 29 years to orbit the Sun. Its traditional domicile is Capricorn and Aquarius. Modern astrology associates it with structure, limits and mastery.
Uranus: Uranus is a planet in the chart. It takes about 84 years to orbit the Sun. Modern astrology gives it Aquarius as its home sign. Modern astrology associates it with change, originality and disruption.
Neptune: Neptune is a planet in the chart. It takes about 165 years to orbit the Sun. Modern astrology gives it Pisces as its home sign. Modern astrology associates it with imagination, dissolution and ideals.
Pluto: Pluto is a planet in the chart. It takes about 248 years to orbit the Sun. Modern astrology gives it Scorpio as its home sign. Modern astrology associates it with transformation, power and depth.
Chiron: Chiron is a small body in the chart. It takes about 51 years to orbit the Sun. Modern astrology associates it with wound, healing and teaching.
North Node: The North Node is a calculated point in the chart. It is the mean lunar node, which moves backward through the zodiac and returns after about 18.6 years. Modern astrology associates it with direction and growth edge.
Lilith: Lilith is a calculated point in the chart. Here it is the mean lunar apogee, the point of the Moon's orbit farthest from Earth. Modern astrology associates it with shadow, autonomy and the unbowed.

Houses

The twelve areas of a chart, and the ways to cut them.

Angular, succedent, cadent: The three kinds of house. Angular houses (1, 4, 7, 10) begin at the four angles, succedent houses (2, 5, 8, 11) follow them and cadent houses (3, 6, 9, 12) precede the next angle.Also: succedent, cadent
Cusp: The line where one house begins and the previous one ends, given as a longitude. The first cusp is the Ascendant.
House: One of twelve divisions of the sky by place and time, used to say in which area of life a body falls. The houses depend on the birth place and moment, and on the house system used.
House system: A rule for cutting the sky into twelve houses. The two systems Genastro offers, Placidus and Whole Sign, agree on the angles and differ on the cusps in between.Also: houses
Placidus: A house system that divides the time each point of the ecliptic takes to travel between the horizon and the meridian. Its houses have unequal sizes, and it cannot be computed beyond the polar circles.
Whole Sign: A house system in which the sign of the Ascendant is the whole 1st house, the next sign the 2nd, and so on. Every house is exactly 30°, and Hellenistic astrologers used it.
1st house: The 1st house covers identity, body and first impressions. It is an angular house, and its natural sign is Aries.
2nd house: The 2nd house covers money, possessions and self-worth. It is a succedent house, and its natural sign is Taurus.
3rd house: The 3rd house covers everyday mind, siblings and local surroundings. It is a cadent house, and its natural sign is Gemini.
4th house: The 4th house covers home, family and roots. It is an angular house, and its natural sign is Cancer.
5th house: The 5th house covers pleasure, romance, play and children. It is a succedent house, and its natural sign is Leo.
6th house: The 6th house covers daily work, health and routine. It is a cadent house, and its natural sign is Virgo.
7th house: The 7th house covers committed relationships and open enemies. It is an angular house, and its natural sign is Libra.
8th house: The 8th house covers shared resources, intimacy, loss and rebirth. It is a succedent house, and its natural sign is Scorpio.
9th house: The 9th house covers travel, higher learning, belief and publishing. It is a cadent house, and its natural sign is Sagittarius.
10th house: The 10th house covers career, reputation and public standing. It is an angular house, and its natural sign is Capricorn.
11th house: The 11th house covers friends, groups and aspirations. It is a succedent house, and its natural sign is Aquarius.
12th house: The 12th house covers the unconscious, solitude, retreat and what is behind the scenes. It is a cadent house, and its natural sign is Pisces.

Aspects

The angles between two bodies.

Applying and separating: An aspect is applying while the two bodies are still closing on the exact angle and separating once they have passed it.Also: separating
Aspect: An angle between two bodies along the ecliptic that matches one of a short list of angles, within an orb. Conjunction, sextile, square, trine and opposition are the five major aspects.
Orb: How far from exact an aspect may be and still count. A square at 91° is within 1° of exact, so a square with an orb of 1°.
Conjunction: A conjunction is an angle of 0° between two bodies, counted when it is within an orb of 8° of exact. It is a major aspect, described as neutral in modern astrology: fusion, emphasis and intensity.
Sextile: A sextile is an angle of 60° between two bodies, counted when it is within an orb of 5° of exact. It is a major aspect, described as easy in modern astrology: opportunity, cooperation and ease.
Square: A square is an angle of 90° between two bodies, counted when it is within an orb of 7° of exact. It is a major aspect, described as hard in modern astrology: tension, friction and drive.
Trine: A trine is an angle of 120° between two bodies, counted when it is within an orb of 7° of exact. It is a major aspect, described as easy in modern astrology: flow, talent and harmony.
Opposition: An opposition is an angle of 180° between two bodies, counted when it is within an orb of 8° of exact. It is a major aspect, described as hard in modern astrology: polarity, awareness and balance.
Quincunx: A quincunx is an angle of 150° between two bodies, counted when it is within an orb of 3° of exact. It is a minor aspect, described as hard in modern astrology: adjustment, mismatch and recalibration.
Semisextile: A semisextile is an angle of 30° between two bodies, counted when it is within an orb of 2° of exact. It is a minor aspect, described as neutral in modern astrology: subtle link, adjacency and friction of neighbors.

Dignities and sect

How traditional astrology rates a planet in a sign.

Detriment: The sign opposite a planet's domicile. Traditional astrology holds that the planet works with difficulty there.
Dignity: The umbrella word for domicile, exaltation, detriment and fall: the traditional ratings of how a planet stands in a sign.
Domicile: The sign a planet rules in traditional astrology, its home. Uranus, Neptune and Pluto carry modern rulerships only.Also: rulership
Exaltation: A sign where traditional astrology holds a planet works especially well. There is no agreed exaltation for the outer planets, Chiron or the calculated points, so Genastro gives none.
Fall: The sign opposite a planet's exaltation. Traditional astrology holds that the planet is weakened there.
Sect: Whether a chart is diurnal (the Sun above the horizon) or nocturnal. Hellenistic astrology sorts the planets into day and night teams on this basis.

Rarity

The words behind the frequency figures.

Frequency: The share of the simulated births that have a placement, such as 7.94% for the Sun in Pisces. "1 in N" is the same figure turned upside down.Also: share, 1 in N
Population weighting: Choosing the simulated birth places in proportion to the populations of cities, so that a birth in Tokyo is far likelier than one in a village. It matters because the Ascendant depends on latitude and longitude.
Rank: The position of a placement among all outcomes of its group, always with its direction named: "2nd rarest of 12" or "26th most common of 144". Rank 1 is the extreme at the end that is named.Also: rarest, most common
Sampling noise: The small random error any sample carries. The more births are simulated, the smaller it is, but it never vanishes: two outcomes whose shares differ by less than the noise are not meaningfully different, which is why close ranks in a large group are shown as "about".
Seasonal and hour curves: Smooth mathematical shapes that make some days of the year and some hours of the day likelier birth moments in the simulation. They are chosen by hand to be plausible and are not fitted to real birth statistics.
Simulated births: A computer-generated sample of birth moments and places, with each chart computed by the real engine. Genastro's frequencies are shares of this sample, not of any register of real births.Also: simulation

Traditions

The schools whose readings the site reports.

Evolutionary astrology: A late 20th-century school that reads the chart as a map of the soul's development, with Pluto and the Moon's Nodes at the center. It frames modern tools in a reincarnation-based worldview.
Hellenistic astrology: The astrology of the Greek-speaking Mediterranean from about the 1st century BCE to the 7th century CE. It reads a chart through Whole Sign houses, sect, dignities and the seven visible planets.
Modern psychological astrology: The 20th-century Western approach, shaped by Jungian psychology. It reads placements as motivations and patterns rather than events, and gives the outer planets full weight.
Traditional (medieval) astrology: The Arabic and Latin astrology of roughly the 8th to the 17th century. Like the Hellenistic school it uses the seven classical planets and judges concrete outcomes.
Vedic astrology: The Indian system of Jyotish. It uses the sidereal zodiac, Whole Sign houses, the 27 nakshatras and the dasha timing systems.Also: Jyotish