Word origin · etymology
French through Middle English, with Latin roots.
Moiety means a half or portion, from Latin medietas. The aspect rule uses a half-share of a planet's orb.
How we know · epistemology
Traditional angular tolerance convention
The arithmetic is reproducible once the orb table is declared. Lilly records alternative values; the resulting tolerance is a traditional selection rule rather than a measured radius of influence.
William Lilly: Christian Astrology (1647), pp. 107 and 110, original text ↗
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.