The Second Layer of Chinese Zodiac Compatibility: the Wu Xing Element Cycle
The 12 Chinese zodiac animals get most of the attention, but every birth year also carries one of five Wu Xing elements — Wood, Fire, Earth, Metal, Water — on a repeating 2-year cycle, and that element interacts with the animal pairing on its own separate axis. Two people whose animals are only "neutral" toward each other can still get a real boost or real friction once their elements are factored in.
The element follows the last digit of the birth year
Synastri reads the element straight off the last digit of the year: 0 and 1 are Metal, 2 and 3 are Water, 4 and 5 are Wood, 6 and 7 are Fire, 8 and 9 are Earth. Two consecutive years always share an element before the cycle moves on — which is also why you sometimes hear both a "Yin" and "Yang" version of the same element/animal pairing described.
The generating cycle: Wood feeds Fire feeds Earth feeds Metal feeds Water
Wu Xing theory arranges the five elements in a fixed generating loop — Wood produces Fire, Fire produces Earth, Earth produces Metal, Metal produces Water, Water produces Wood, and back to Wood. Synastri's `chinese-zodiac/compatibility` calculator checks where each person's element sits in that loop: the same element on both sides gets a small positive bonus, one element generating the other gets a bigger bonus (the strongest element interaction in the system), and any other pairing — skipping ahead or sitting unrelated in the cycle — gets a penalty.
Why it's a separate score from the animal relationship
The animal side (harmony triads, direct conflicts, and the neighboring-animal "sextile" bonus) and the element side are computed independently and then added together, so a triad match with a clashing element pair isn't automatically a top score, and a merely-neutral animal pairing with a generating element relationship isn't automatically weak. Check your own combined score on `/chinese-zodiac/compatibility`. For entertainment.