fickle

形容词 fickle:

1. marked by erratic changeableness in affections or attachments
   同义词：volatile
2. liable to sudden unpredictable change
   同义词：erratic, mercurial, quicksilver

1. It's the third time that he changed his mind; he's so fickle!
   ＂他改变主意已经是第三回了，他这人太反复无常了！＂
2. Fortune's fickle wheel.
   多变的命运之轮。
3. He turned out to be fickle - he has left me.
   他原来是个善变的人 - 他离开我了。

fick.le

adj.（形容词）
Characterized by erratic changeableness or instability, especially with regard to affections or attachments; capricious.
无常的，易变的：表现为无规律的变化或者不稳定性的，尤指在感情或爱慕方面；反复无常的

来源：
Middle English fikel
中古英语 fikel
from Old English ficol [deceitful]
源自 古英语 ficol [欺骗的]

【引伸】
fick.leness
n.（名词）
fick.ly
adv.（副词）