NatalCalculator

Astrology Glossary: Every Term This Site Uses

An astrology glossary built to be scanned rather than read: short, exact definitions for every term this site uses, in astrology and in the astronomy underneath it.

Several entries below cover terms specific to Vedic astrology, including ayanamsa, nakshatra and dasha. Those three are computed in practice by the sidereal chart calculator.

Every term, A to Z

Ascendant
The zodiac degree rising on the eastern horizon at the exact moment of birth, marking the cusp of the first house. It sets the entire house wheel and is often described as the mask or manner a person presents to the world.
Ayanamsa
The angular offset between the tropical and sidereal zodiacs, produced by the slow wobble of Earth’s axis known as precession. This site’s Vedic calculator applies the Lahiri ayanamsa, currently a gap of roughly 24 degrees.
Big Three (Sun, Moon, Rising)
Shorthand for the three placements most people learn first: the Sun sign (core identity), Moon sign (emotional temperament), and Ascendant or Rising sign (outward demeanor). Together they give a quick sketch of a chart before the finer detail is added.
Chart ruler
The planet that rules the sign on the Ascendant, treated as a kind of narrator for the whole chart. Its sign, house, and aspects are read as commentary on how the native pursues their overall life direction.
Composite chart
A single chart built from the mathematical midpoints between two people’s planetary positions, used to study a relationship as its own entity rather than comparing two individual charts side by side.
Cusp
The boundary line where one house or one zodiac sign ends and the next begins. Someone born very close to a cusp may show a blend of traits from both signs or houses on either side of that line.
Dasha
A Vedic astrology timing system that divides a lifetime into sequential planetary periods, each ruled by a different planet, used to forecast when particular themes are likely to become active. See Vimshottari for the specific model used here.
Degree (of a sign)
Each zodiac sign spans 30 degrees of the 360-degree ecliptic, and a planet’s exact position is expressed as a degree within its sign, such as 14 degrees Leo. Precise degrees matter for calculating aspects and house cusps.
Element (fire, earth, air, water)
One of four groupings that classify the twelve signs by temperament: fire signs act on instinct, earth signs favor the practical, air signs process through ideas, and water signs respond through feeling.
Ephemeris
A table or dataset listing the calculated positions of the Sun, Moon, and planets for a given range of dates and times. Chart-casting software, including this calculator, draws on ephemeris data to place planets accurately.
Grand Trine
A configuration in which three planets each sit roughly 120 degrees apart, forming a closed triangle of trine aspects, usually within one element. It suggests an area of natural ease that can, without effort, go untested.
House system
The mathematical method used to divide the chart into twelve houses from a given birth time and location. Different systems, such as Placidus or Whole Sign, can assign the same planet to different houses even from identical birth data.
Inter-chart aspect
An angular relationship formed between a planet in one person’s chart and a planet in another person’s chart, the building block of synastry analysis, distinct from an aspect formed entirely within a single natal chart.
Lahiri
A widely used ayanamsa named after the Indian astronomer N.C. Lahiri, adopted as India’s official standard for sidereal calculations. It is the ayanamsa this site’s Vedic calculator uses to convert tropical positions into sidereal ones.
Midheaven (MC)
The point where the ecliptic crosses the meridian directly overhead at the moment of birth, forming the cusp of the tenth house; also called the MC, from the Latin Medium Coeli. It is commonly tied to career, public standing, and reputation.
Modality (cardinal, fixed, mutable)
A second classification of the twelve signs describing how they operate: cardinal signs initiate, fixed signs sustain and stabilize, and mutable signs adapt and transition. Every sign carries one element and one modality.
Nakshatra
One of 27 lunar mansions used in Vedic astrology, each spanning 13 degrees 20 minutes of the sidereal zodiac. The Moon’s nakshatra at birth carries its own ruling deity, symbol, and temperament separate from its sign.
Natal (chart)
Describing a chart cast for the precise moment and location of birth, capturing a fixed snapshot of the sky that serves as the baseline against which transits and progressions are later measured.
Node (lunar node / North Node / South Node)
One of two points where the Moon’s orbit crosses the ecliptic. The North Node points toward unfamiliar growth the native is drawn to develop, while the South Node, its exact opposite, marks inherited habits and comfortable default patterns.
Orb
The margin of error, measured in degrees, allowed on either side of an aspect’s exact angle before it still counts as active. A tighter orb signals a more precise, and generally stronger, aspect.
Placidus
A time-based house system, the most common one in modern Western astrology, that divides the chart using the diurnal motion of degrees along the ecliptic rather than dividing it into equal arcs.
Progression
A symbolic, slow-moving technique for advancing a natal chart forward in time to track inner development. Secondary progressions, the most common method, equate one day of ephemeris movement after birth with one year of life.
Rectification
The practice of narrowing down an unknown or uncertain birth time by working backward from documented life events, testing candidate charts until the timing of major transits and progressions lines up with what actually happened.
Retrograde
The apparent backward motion of a planet through the zodiac as seen from Earth, an optical effect of differing orbital speeds rather than an actual reversal. Periods of retrograde motion are traditionally read as times for review rather than fresh starts.
Saturn return
The roughly 29.5-year cycle in which transiting Saturn arrives back at the exact degree it occupied at birth, falling near ages 29-30, 58-59, and 87-88. Each pass is associated with a reckoning around maturity, structure, and responsibility.
Sidereal
A zodiac system anchored to the actual, observable positions of the constellations rather than to the seasons. Vedic astrology uses the sidereal zodiac, which currently sits roughly 24 degrees behind its tropical counterpart.
Stellium
A cluster of three or more planets occupying the same sign or the same house. It concentrates emphasis in one area of life or one mode of expression, often to the point of dominating the rest of the chart.
Synastry
The comparative technique of overlaying two individual charts to examine the aspects formed between them, used to assess compatibility and the dynamics likely to arise between two people.
T-square
A pattern formed by two planets in opposition, each also square to a third planet, creating a tense right-triangle shape. The planet at the apex, receiving both squares, tends to concentrate the pressure into a single, action-forcing focal point.
Transit
The current, real-time position of a planet in the sky, compared against the fixed positions of a natal chart to time present-day events. Unlike a progression, a transit reflects where a planet actually is right now.
Tropical
A zodiac system fixed to the seasons, with 0 degrees Aries defined by the spring equinox rather than by constellation boundaries. Most Western astrology relies on the tropical zodiac, which has drifted from the sidereal one over centuries of precession.
Vimshottari
The dominant dasha system in Vedic astrology, dividing a 120-year life cycle into nine planetary periods of fixed length based on the Moon’s nakshatra at birth. This site’s Vedic calculator relies on Vimshottari for its timing forecasts.
Whole Sign houses
An ancient house system in which an entire sign equals one house, with the sign containing the Ascendant becoming the whole first house regardless of the Ascendant’s exact degree. It predates and differs from degree-based systems like Placidus.
Yod
A configuration nicknamed the "Finger of Fate," formed by two planets sextile each other, both linked by quincunx aspects to a third planet at the apex. It points to a specialized, sometimes uncomfortable, area of destined focus.

How to use this glossary

Each entry is written to be read on its own, in one or two sentences, without needing the entry above it. Every definition has its own anchor, so a link to a single term lands on that term rather than at the top of the page, and the rest of this site links here that way whenever a term first appears. Where a word means one thing in Western practice and something else in Vedic practice, the entry says which is which rather than blending them into a single vague gloss.

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