四柱八字（Bazi，或测 Eight Characters）是中国命理体系的核心之一，它把一个人的出生时间换算成年、月、日、时四组干支（每组由“天干+地支”各一个组成），合称“四柱”，共八个字，故称“八字”。
BaZi (Four Pillars) is a core tradition of Chinese fate theory. It converts your birth date and time into Year, Month, Day, Hour pillars — each a pair of a Heavenly Stem and an Earthly Branch — eight characters in total.
天干有甲、乙、丙、丁、戊、己、庚、辛、壬、癸，五行分属木、火、土、金、水；地支有子、丑、寅、卯、辰、巳、午、未、申、酉、戌、亥，并对应十二生肖。
There are 10 Heavenly Stems and 12 Earthly Branches (also the zodiac animals). Stems assign the Five Elements — Wood, Fire, Earth, Metal, Water — to your chart.
以日柱（日主）为“我”，其它干支与我的五行生克关系化作十神：比肩、劫财、食神、伤官、偏财、正财、七杀、正印、偏印、正官。十神组合常被用来解读性格倾向与亲缘、事业、财帛等关系。
Treating the Day Master as "me," the other stems interact with it via the Five Elements to form Ten Gods — often used to explore personality, career, wealth, and relationships in a reflective way.