Something that is fun provides enjoyment or amusement. Something that is convivial is friendly and agreeable, or festive. Convivial is a warm and social term; it's most often used to talk about gatherings of people who are in high spirits and enjoying one another's company, often sharing in a meal or refreshments. Its gregarious nature makes sense given its origin: convivial comes from the Latin noun convīvium meaning "feast," which derives from the verb convīvere "to live together, to dine together." When describing a person, convivial means "merry company, jovial." Convivial is good company any time of year, but given its appetite for feasting and gathering, it's no wonder we hear convivial a little more around the holidays!

To improve something is to make it better or bring it into a more desirable condition. Ameliorate shares this broad sense, but this formal verb is typically used to discuss circumstances that are more dire than what you might find with improve. For instance, you may hear of improving a workflow, or improving sound quality, but it is less likely that you'll hear ameliorate used in everyday contexts such as these. More commonly, you'll find ameliorate in discussion of oppressive, unjust, or difficult conditions, such as those brought by social or economic inequality or environmental degradation.

When a task or duty is so difficult to perform that doing so feels like a burden, it may be best described as onerous. Onerous comes from the Latin word for "burden," onus, which is used in English with the same meaning. A burden is something that is oppressively heavy, and indeed, when we use the word onerous, we evoke the idea of heaviness: an onerous undertaking is one so riddled or "heavy" with hardships it is difficult to bear. Onerous is also used to describe agreements, contracts, or guidelines that are so bogged down with legal obligations or restrictions, the intended benefits or advantages are outweighed.