Which operator would you use to negate a condition in a MongoDB query?

The operator that is used to negate a condition in a MongoDB query is indeed the $not operator. This operator allows you to specify a condition that must not be true for the documents that the query retrieves. By using $not, you can effectively reverse the logic of the condition applied, allowing for more complex querying capabilities.

For example, if you want to find documents where a specific field does not equal a certain value, you could use $not to specify that condition. This operator is particularly useful when you want to filter out documents that meet certain criteria, ensuring that only those that do not meet the specified condition are returned in the result set.

In contrast, other operators like $or and $and are used to combine multiple conditions rather than negate them. The $or operator returns documents that satisfy at least one of the specified conditions, while the $and operator requires that all specified conditions are met. The $elemMatch operator is specifically designed for matching elements within an array, and it's not intended for negation purposes. Thus, $not is the appropriate choice when you want to negate a condition in a MongoDB query.