The phrase "are sure" is commonly used to express certainty or confidence. However, there are various synonyms that one can use interchangeably with this phrase. For instance, one can say "are certain," "are confident," "are convinced," or "are positive" to convey the same message. Other synonyms include "are surefire," "are unambiguous," "are unquestionable," and "are indisputable." These synonyms can be used in different contexts, such as in business, academics, or social settings. It is important to choose the appropriate synonym that best fits the situation to effectively communicate one's thoughts and ideas.