The adjective 'earnest' means to come from an intense and serious state of mind. If you are earnest it means your intentions are serious or purposeful, that you are sincere or that something deserves to be considered seriously. As a noun 'earnest' means full of seriousness, purpose or intention.

1. I surprised a lot of people with my comments yesterday. I don't think anyone could work out whether I was speaking in earnest or in jest.
2. You seem to be very earnest to start studying, but if I were you I would enjoy the summer holiday first.

1. Today was just a trial day so you could learn the ropes. Your work begins in earnest on Monday morning!
2. The two companies need to stop playing games. If they really want to get a deal done then they need to sit down and negotiate in earnest.
3. When my employees come to me in earnest with a problem or issue, I take it seriously and listen to their concerns.