Word origin · etymology
Latin borrowing.
Vertex meant a turning point, crown of the head, or summit, from vertere, to turn; astrology applies it to a particular intersection.
How we know · epistemology
Local spherical geometry
The ecliptic–prime-vertical intersection can be calculated for a place and instant. Treating a contact to it as a destined encounter is an interpretive claim, not a property measured by the geometry.
Connected concepts
Terms used in this explanation
These links connect subjects and terminology. They do not establish a shared historical origin.
Sources & provenance
Use the citations beside each section to distinguish a calculation convention, a historical teaching and an editorial example.