形容詞 fain:

1. having made preparations
   同義詞：disposed, inclined, prepared

副詞 fain:

1. in a willing manner
   同義詞：gladly, lief

1. I would fain help you.
   我樂意幫助你。
2. Men and birds are fain of climbing high.
   不論人還是鳥都愿意往高處攀。
3. I would fain go with you.
   我高興和你一起去。

fain

adv.（副詞）
Happily; gladly:
幸福地；樂意地：
例句：
.I would fain improve every opportunity to wonder and worship, as a sunflower welcomes the light.(Henry David Thoreau)
.我將像向日葵迎接太陽那樣樂意在每一個機(jī)會贊美和崇拜（它）.(亨利·戴維·梭羅)

Archaic Preferably; rather.
【古語】 寧愿；寧可
adj.Archaic （形容詞）【古語】
Ready; willing.
愿意的；樂意的
Pleased; happy.
高興的；幸福的
Obliged or required.
被迫的，要求的

來源：
Middle English
中古英語
from Old English fôgen [joyful, glad]
源自 古英語 fôgen [高興的，快樂的]