Earnest
Definition 1 of 3
Pro Tip 1/3
Not playful
Use 'earnest' to describe someone's behavior when they are not joking and mean what they say. His apology was in earnest; he really was remorseful.
Pro Tip 2/3
Convey respect
'Earnest' often shows respect for the subject or situation being discussed due to the sincere approach. Her earnest speech at the ceremony moved everyone.
Pro Tip 3/3
Emotional weight
When someone speaks in earnest, they convey a sense of importance and concern. Listen to me in earnest; this matter affects us all.