The search began in earnest when the police arrived.警察到达后，开始了认真的搜寻。

It began to rain in earnest [=heavily] in the evening.晚上，雨开始下大了。

It's hard to tell if he's making this proposal in earnest.很难说他提出这个建议是否是认真的。

We thought he was joking at first, but then we realized that he was in earnest. [=he was being serious]我们一开始还以为他在开玩笑，但后来意识到他是认真的。