Reference
Astrology Glossary
A-Z reference for every astrology term used across NatalChart.AI — from arc-second to zodiac.
A
- Angular house
- 1st, 4th, 7th and 10th houses — the houses anchored to the chart's four angles. Strongest by traditional weighting.
- Applying aspect
- An aspect moving toward exactness — the faster body is closing the angular gap with the slower body. Often feels future-leaning.
- Arc-second
- 1/3600 of a degree. Swiss Ephemeris reproduces JPL ephemeris data at 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.
- 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°).
- 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
- The mean lunar apogee — the empty focus of the Moon's orbit. Read as the unowned, exiled feminine in modern astrology.
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 constrained at the prompt level to only explain factors that appear in the calculated chart payload.
- 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 — a launch, a contract, 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
- 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).
- House system
- The method used to divide the sky into twelve houses. Placidus is the most widely used in modern western astrology and the NatalChart.AI default.
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.
- Inter-chart aspect
- An aspect between a body in one chart and a body in another. The basic unit of synastry.
J
- JPL Development Ephemeris (DE431)
- NASA Jet Propulsion Laboratory's high-precision planetary ephemeris. Swiss Ephemeris is built on it.
- 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
- 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 — North Node (Rahu) and South Node (Ketu). 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.
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 tolerance allowed around an exact aspect angle. A square within 8° still reads as a square; outside that orb the aspect is too weak.
P
- Part of Fortune
- A calculated point — for day births: Asc + Moon - Sun. Marks a place of innate flow or good.
- Placidus system
- A quadrant-based house system that splits the time-arc the Sun travels between horizon and meridian into thirds. The most widely used modern western house system.
- 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 that has passed exactness and is widening. Often feels like a completed arc.
- 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 life-sphere model: Self, Heart, Body, Matter, Roots, Mind. Each sphere has a relevance vector across chart factors.
- 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, built on JPL DE431, used by NatalChart.AI for all chart calculation.
- 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.