名詞 eighth:

1. position eight in a countable series of things
2. one part in eight equal parts
   同義詞：one-eighth

形容詞 eighth:

1. coming next after the seventh and just before the ninth in position
   同義詞：8th

1. The eighth day after a feast day, counting the feast day as one.
   第八天教會(huì)節(jié)日后從該日算起的第八天
2. One of the four brightest satellites of Jupiter and the eighth in distance from the planet. Originally sighted by Galileo, it is one of the largest satellites in the solar system.
   木衛(wèi)三木星四顆最亮的衛(wèi)星之一，距木星的遠(yuǎn)近程度是第八位。最早伽利略觀察到，是太陽(yáng)系最大的衛(wèi)星之一
3. One eighth of a circle.
   八分圓圓的八分之一
4. August is the eighth month in a year.
   八月是一年中的第八個(gè)月。

eighth

n.（名詞）
The ordinal number matching the number eight in a series.
第八：在一列中對(duì)應(yīng)于8的序數(shù)
One of eight equal parts.
八分之一：八個(gè)相等部分之一

來(lái)源：
Middle English eighthe
中古英語(yǔ) eighthe
from Old English eahtotha
源自 古英語(yǔ) eahtotha
from eahta [eight] * see oktô(u)
源自 eahta [八] *參見 oktô(u)

【引伸】
eighth
adv.（副詞）
adj.（形容詞）