* Above: This is the most common opposite, meaning "higher than." For example, "The bird is flying above the tree" is the opposite of "The bird is flying under the tree."
* Over: This also means "higher than" but can imply a sense of covering or encompassing. For example, "The blanket is over the bed" is the opposite of "The blanket is under the bed."
* On: This means "directly on top of" and can be used when something is resting on a surface. For example, "The book is on the table" is the opposite of "The book is under the table."
* Upon: Similar to "on," this means "directly on top of" but is more formal. For example, "The crown is upon the king's head" is the opposite of "The crown is under the king's head."
* Above: This means "higher than," but specifically in terms of position or rank. For example, "He is above me in the company hierarchy" is the opposite of "He is under me in the company hierarchy."
The best opposite will depend on the specific situation you're describing.