A conjunction is an apparent close approach of two celestial bodies when seen from a specific vantage point, most commonly the Earth. In both astronomy and astrology the term describes proximity in the sky rather than physical proximity in space. The same visual event can be called an appulse; under special circumstances it may lead to an occultation or an eclipse when one body passes in front of another.
Definition and geometry
Astronomically, a conjunction usually refers to two objects sharing the same celestial longitude or right ascension as projected onto the sky from the observer’s point of view. Because observers occupy different places, a conjunction defined from the centre of the Earth (geocentric) can differ slightly from a topocentric conjunction seen by an observer on the surface. Parallax and the chosen coordinate system determine the precise timing.
Types and observational notes
- Conjunction with the Sun: For planets, 'inferior' and 'superior' conjunctions describe inner and outer planet alignments relative to the Sun’s position.
- Planet–planet conjunctions: Two planets appear near one another; close pairings of bright planets are easily visible and often attract public interest.
- Moon conjunctions: When the Moon passes near another body it can mark a new moon (Moon–Sun conjunction) or a close approach to a planet or star.
- Occultation vs appulse: A conjunction may be a simple apparent approach (appulse) or, if alignment is precise, an occultation when one body hides another.
Examples and significance
Conjunctions are common and vary from routine lunar-planet approaches to rare events such as very close pairings of the giant planets. Astronomers use conjunctions to schedule observations and to calibrate positional measurements; for casual observers they can provide striking views when two bright bodies share the same field of view through binoculars or a telescope.
Conjunction in astrology and symbol
In astrology, a conjunction is one of the primary aspects and is thought to represent a blending or intensification of the involved bodies’ qualities. Interpretations differ by tradition and practice and are not matters of empirical science. The conventional symbol for conjunction is shown here: 
Distinctions matter: conjunctions are defined from a chosen viewpoint and contrast with oppositions or greatest elongation, which describe other angular relationships. Whether studied for predictive traditions, positional astronomy, or simple skywatching, conjunctions remain a basic and widely observed class of celestial events.