When expressing certainty, we often use the phrase "am sure about." However, there are many other synonyms you can use to replace this phrase and add more variety and depth to your language. Instead of "am sure about," you can say "absolutely certain," "confident," or "convinced." Other options include "positive," "assured," and "secure." If you want to convey a stronger sense of conviction, try "unwavering," "rock solid," or "firmly believe." Whatever phrase you choose, using synonyms can help you communicate your thoughts more effectively and make your language more interesting and engaging.