(八相) also 八相示現 Eight aspects of the Buddha's life, which the 起信論 gives as: (1) descent into and abode in the Tuṣita heaven; (2) entry into his mother's womb; (3) abode there visibly preaching to the devas; (4) birth from mother's side in Lumbinī; (5) leaving home at 19 (or 25) as a hermit; (6) after six years' suffering attaining enlightenment; (7) rolling the Law-wheel, or preaching; (8) at 80 entering nirvāṇa. The 四教義 group of Tiantai is slightly different — descent from Tuṣita, entry into womb, birth, leaving home, subjection of Māra, attaining perfect wisdom, preaching, nirvana. See also the two 四相, i.e. 四本相 and 四隨相.
佛示現人間,有八種相,名八相成道。成道雖只是八相之一,但也是八相中的主腦,故特標成道之名。大乘所說的八相是:降兜率、入胎、住胎、出胎、出家、成道、轉法輪、入滅。小乘所說的八相是從兜率天下、託胎、出生、出家、降魔、成道、轉法輪、入涅槃。此中大乘有住胎,無降魔,小乘有降魔,無住胎。
(名數)佛陀以成道為中心,示現由始至終一期之相狀,謂之八相成道。成道雖為八相中之一,然為八相中之主腦,故別揭成道之名。八相經論所說存沒不同,而大要有二說。大乘起信論所說者,一、降兜率,先住於兜率天,在彼天四千歲。見時機熟,遂乘白象由彼天降下之相也。二、入胎,乘白象由摩耶夫人左脅入胎之相也。三住胎,在母胎行住坐臥一日六時為諸天說法之相也。四出胎,四月八日於藍毘尼園由摩耶右脅出生之相也。五出家,十九歲(或二十五歲)觀世之無常,出王宮入山學道之相也。六成道,經六年苦行,在菩提樹下成佛得道之相也。七轉法輪,成道以後五十年間說法普度人天之相也。八入滅,八十歲在娑羅雙樹下入於涅槃之相也。起信論曰:「隨其願力能現八種,利益眾生。所謂從兜率天退、入胎、住胎、出胎、出家、成道、轉法輪、入於涅槃。」天台大師之四教儀,除第三之住胎,加入第五降魔之相為八相。四教儀四曰:「釋菩薩位略為七位:一發菩提心、二行菩薩道、三種三十二相業、四六度成滿、五一生補處、六生兜率天、七八相成道。(中略)所言八相成道者:一、從兜率天下,二、託胎,三、出生,四、出家,五、降魔,六、成道,七、轉法輪,八、入涅槃。古來以此二說為大小乘之別,初為大乘之八相,後為小乘之八相,然此二種八相,僅開合不同耳,非區別二乘也。」佛祖統紀二曰:「述曰:大乘開住胎合降魔於成道,小乘開降魔合住胎於託胎。住胎見起信,降魔見四教儀,此先達之論也。今觀大小皆有住胎降魔之文,如華嚴云菩薩住母胎已,示現出家成道等相,此大乘住胎也。因果經,菩薩在母胎行住坐臥,一日六時,為諸天鬼神說法,此小乘住胎也。華嚴離世間品菩薩出家成道降魔轉法輪等。妙樂云:四德各有四降魔相,此大乘降魔也。因果經,既降魔已,即便入定,明星出時,得最正覺,此小乘降魔也。今欲順八相之言,且用起信四教儀二文開合為證。」