assiduously
adverb/əˈsɪdʒuəsli/
/əˈsɪdʒuəsli/
(formal)- in a way that involves working very hard and taking great care
- They worked assiduously to earn the money for their son’s education.
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assiduously
Definition of assiduously adverb from the Oxford Advanced Learner's Dictionary