1. 善变,变幻无常：out of the blue始料未及的 ≈ unexpected | fickleness 善变,变幻无常 | pandemic 全球流行病

2. 易变：countless 无数的 | fickleness 易变 | closeness 紧密;严密,精密

3. 变化无常：she was difficult to please. 很难让她称心如意 | fickleness变化无常 | unrelenting不屈不挠的、不松懈的

noun

1. unfaithfulness by virtue of being unreliable or treacherous

    Synonym: faithlessnessfalsenessinconstancy