A
- Angular house
- The 1st, 4th, 7th and 10th houses: the houses anchored to the chart's four angles. Strongest by traditional weighting.
- Applying aspect
- An aspect whose orb is closing, so the two bodies are moving toward the exact angle. Whether it is closing follows from the motion of both bodies, retrograde included, not from the faster one alone. NatalChart.AI calculates this for each natal and transit aspect.
- Arc-second
- 1/3600 of a degree. Swiss Ephemeris computes planetary positions to this precision.
- Ascendant (Asc)
- The zodiac degree rising on the eastern horizon at the moment of birth. Cusp of the 1st house. Sensitive to exact birth time: without one it is undetermined, not approximate.
- Aspect
- An angular relationship between two bodies in a chart. The five major aspects are conjunction (0°), sextile (60°), square (90°), trine (120°), opposition (180°). NatalChart.AI calculates these five only.
- Astrocartography
- Mapping where each planet was angular at the moment of birth onto the world map. Lines indicate places where each planet's themes are amplified.
B
- Black Moon Lilith
- A calculated point at the Moon's apogee, the far point of its orbit. NatalChart.AI uses the osculating (true) apogee; other tools use the mean apogee, and the two can differ by several degrees. It is a geometric point, not the second focus of the orbit and not the asteroid 1181 Lilith. Read in modern astrology as the unowned, exiled feminine.
- Body (sphere)
- One of NatalChart.AI's six life spheres: energy, sleep and health. Read from Sun, Mars, Chiron and Pluto; the 6th house; the Ascendant.
C
- Chart-Grounded AI Astrology
- The practice of grounding every AI interpretation in a calculated chart's structured data, rather than improvising from sun-sign archetypes.
- Chart-Locked AI Reading
- NatalChart.AI's branded implementation of chart-grounded AI: the language model is instructed, at the prompt level, to explain only factors that appear in the calculated chart data. The instruction lowers the risk of an invented factor; it does not remove it.
- Chiron
- A small body between Saturn and Uranus, read in modern astrology as 'the wound that becomes the medicine'.
- Composite chart
- A chart computed from the midpoints of two natal charts, used as a third chart describing the relationship itself.
- Conjunction
- 0° aspect. Two bodies at the same zodiac longitude: energies fuse.
- Cusp
- The boundary between two houses or signs. House cusps are computed for each chart from latitude and local sidereal time.
D
- Descendant (Dsc)
- Cusp of the 7th house, opposite the Ascendant. The mirror in the other.
E
- Ecliptic
- The plane of Earth's orbit around the Sun, projected onto the sky. The zodiac is a 360° band along this plane.
- Electional astrology
- Choosing a favourable moment for an important act, such as a launch, a contract or a difficult conversation, by examining the chart of that moment.
- Ephemeris
- A table or computation of celestial body positions over time. Without one, software cannot know where a planet was at a given moment.
F
- Fixed star
- A non-planetary star whose position stays close to constant against the background. Astrology reads conjunctions to chart factors with tight orbs (~1.5°).
H
- Home (sphere)
- One of NatalChart.AI's six life spheres: family, the home and parents. Read from Moon, Saturn, Ceres and Juno; the 4th house.
- House
- One of twelve sectors of the chart, each tied to a life domain (self, resources, mind, roots, heart, body, partners, depth, meaning, vocation, community, the hidden). Houses depend on the exact birth time and place; without a birth time they are undetermined, not approximate.
- House system
- The method used to divide the sky into twelve houses. Placidus is the most widely used in modern western astrology and the only one NatalChart.AI calculates.
I
- IANA Time Zone Database
- The canonical historical timezone database. Used to convert local birth time to UTC, including past DST and offset rules.
- IC (Imum Coeli)
- Cusp of the 4th house, the lowest point of the chart, opposite the Midheaven. Inner foundation, home of origin.
- Identity (sphere)
- One of NatalChart.AI's six life spheres: who you are and the direction you take. Read from Sun, Moon, Pluto and True Node; the 1st house; the Ascendant and Midheaven.
- Inter-chart aspect
- An aspect between a body in one chart and a body in another. The basic unit of synastry.
J
- Julian Day
- A continuous count of days used in astronomical calculation. NatalChart.AI converts birth UTC to Julian Day before passing it to Swiss Ephemeris.
L
- Love (sphere)
- One of NatalChart.AI's six life spheres: love, friendship and the hard conversations. Read from Venus, Moon, Mars, Juno, Vesta, Lilith and Neptune; the 5th and 7th houses.
- Luminaries
- The Sun and Moon, traditionally distinguished from the rest of the planets by their reflective importance to a chart.
- Lunar Node (True Node)
- The points where the Moon's orbit crosses the ecliptic: the North Node (Rahu) and the South Node (Ketu). NatalChart.AI calculates the true node, not the mean node; the two can differ by more than a degree. Read as direction of growth and where you've come from.
M
- Midheaven (MC)
- Cusp of the 10th house, the highest point of the chart at birth. Public role, vocation.
- Mind (sphere)
- One of NatalChart.AI's six life spheres: thinking, learning and ideas. Read from Mercury, Uranus, Pallas and Jupiter; the 3rd and 9th houses.
- Money (sphere)
- One of NatalChart.AI's six life spheres: career, finances and work. Read from Venus, Jupiter, Saturn and Ceres; the 2nd, 6th and 10th houses; the Midheaven and Part of Fortune.
N
- Natal chart
- A chart cast for the moment, place and date of birth. The base reference for most astrology.
O
- Opposition
- 180° aspect. Two bodies face each other across the chart: polarity, projection, integration challenge.
- Orb
- The distance of an aspect from exact, in degrees, and the tolerance a tool allows before it stops listing the aspect. NatalChart.AI uses fixed natal orbs: 8° for a conjunction, square, trine and opposition, 6° for a sextile. The orb is named with the aspect because a square 0°30′ from exact and a square 7°30′ from exact are both squares and are not the same thing.
P
- Part of Fortune
- A calculated point. NatalChart.AI uses ASC + Moon − Sun for every chart, day and night alike. The traditional rule swaps Sun and Moon for a night birth; the two formulas can land in the same sign or in different ones. Read as a place of innate flow or good.
- Placidus system
- A quadrant-based house system that divides the diurnal and nocturnal arcs of points on the ecliptic, the time a degree spends between the horizon and the meridian, into thirds; the Ascendant is the 1st cusp and the Midheaven the 10th. The most widely used modern western house system, and the one NatalChart.AI calculates.
- Planet
- In astrology, any moving body in the chart, including the Sun and Moon (the luminaries). Inherited from pre-Copernican usage.
- Pluto
- A transpersonal body whose astrological themes are death-rebirth, depth, and what cannot stay surface.
R
- Relocation chart
- A natal chart recomputed as if the person had been born in a different city, at the same UTC moment. Houses and angles shift; planet zodiac positions stay.
- Retrograde
- Apparent backward motion of a planet from Earth's perspective. Read in astrology as a slowing or interiorising of that planet's themes.
S
- Separating aspect
- An aspect whose orb is opening, so the two bodies are moving away from the exact angle, judged by the motion of both bodies. NatalChart.AI calculates this for each natal and transit aspect.
- Sextile
- 60° aspect. A soft opportunity: easy cooperation between two bodies, but requires effort to use.
- Sidereal time
- Time measured by the position of stars rather than the Sun. Used to compute the Ascendant and house cusps for a given location and moment.
- Six spheres
- NatalChart.AI's six areas of life: Identity, Love, Body, Money, Home, Mind. Each is read from a fixed set of planets, houses and points of the chart. Where a sphere carries a score (the week, a year, a place, two charts), the number comes from a fixed rule over aspects and house positions and is not a probability of an event.
- Solar Return
- The exact moment the transiting Sun returns to its natal zodiac degree. The Solar Return chart cast for the current location is used to read the year ahead.
- Square
- 90° aspect. A hard friction-and-drive aspect that builds skill through recurring tension.
- Sun sign
- The zodiac sign the Sun was in at birth. Often confused with 'star sign'. The Sun sign is one factor among many in a full chart.
- Swiss Ephemeris
- The high-precision ephemeris computation library originally developed by Astrodienst, used by NatalChart.AI for all chart calculation. NatalChart.AI runs version 2.10.03 with the Swiss Ephemeris data files.
- Synastry
- Comparing two natal charts to study the relationship between them. Looks at inter-chart aspects and house overlays.
T
- Transit
- The current real-time position of a planet aspecting a planet in your natal chart. Marks a period when a particular theme is touching a specific area of life.
- Transpersonal planet
- Uranus, Neptune or Pluto. Slow-moving generational bodies whose personal expression depends on the house and aspect they make to faster planets.
- Trine
- 120° aspect. A soft flow-and-talent aspect: easy current between two bodies, sometimes so easy it's taken for granted.
V
- Vertex
- A calculated sensitive point on the western side of the chart. Read in modern astrology as a fated encounter or unexpected door.
W
- WGS 84 / EPSG:4326
- The geodetic standard for latitude/longitude in decimal degrees. NatalChart.AI uses it for all birthplace coordinates.
Z
- Zodiac
- The 360° band along the ecliptic, divided into twelve equal 30° signs. Each planet's position is reported as a degree within a zodiac sign. NatalChart.AI uses the tropical zodiac, which starts at the March equinox; a sidereal zodiac starts from a point fixed against the stars, about 24 degrees away today.