The antonyms for the word "light heartednesses" are serious, grave, somber, intense, heavy, sober, and solemn. These words represent the opposite of light heartednesses which is a state of being carefree, joyful, and lighthearted. Serious describes a situation where something is worthy of attention and consideration because it involves significant consequences. Grave refers to a situation or event that is serious, somber, or solemn. Intense, heavy, and solemn describe situations that are deep, serious, and filled with significant emotion. Sober refers to a situation where one is not under the influence of alcohol or drugs, but it can also refer to a serious or solemn attitude.