very serious and sincere 非常认真的；真诚的 an earnest young man 非常认真的年轻人 Despite her earnest efforts, she could not find a job. 尽管她已尽心竭力，但是仍然找不到工作。 When I looked over, he was in earnest conversation with his father. 当我看过去的时候，他正在和他的父亲认真地交谈。 She was nice enough, but perhaps a little too earnest. 她人很好，但可能有点太认真了。
Oxford Collocations DictionaryEarnest is used with these nouns:- desire
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Word OriginOld English eornoste (adjective), eornost (noun), of Germanic origin; related to German Ernst (noun).
Idioms
in earnest
more seriously and with more force or effort than before （更加）严肃地，认真地，坚定地 The work on the house will begin in earnest on Monday. 这栋房子的修建工作将在星期一正式开始。 That was when our troubles started in earnest. 那是我们的麻烦真正开始的时候。
very serious and sincere about what you are saying and about your intentions; in a way that shows that you are serious 郑重其事；当真