In Chinese (especially Buddhist-influenced) folk thought, romantic and karmic relationships are often explained as
前缘 — a connection carried over from a previous life. The phrase
前缘未了 (qiányuán wèi liǎo, 'past-life ties not yet ended') is a common romantic-drama trope.
缘 also means 'edge', which gives the technical sense — leading edge of an airplane wing or blade.
