When someone is said to be doing something "in earnest," it means they are doing it with genuine intention and effort. There are many synonyms that can be used in place of this phrase, such as "seriously," "earnestly," "determinedly," "sincerely," "wholeheartedly," "committedly," and "resolutely." Each of these words conveys a sense of focused determination and sincerity, and can be used in a variety of contexts to describe someone who is working hard to achieve their goals. Whether you are striving to complete a difficult task or pursuing your dreams, using synonyms for "in earnest" can help you communicate your commitment and dedication to others.