The phrase "made certain" refers to ensuring or making sure of something. There are several synonyms for this phrase that can be used interchangeably, such as confirmed, verified, validated, established, guaranteed, and affirmed. These words can indicate a level of certainty and reliability in the information being conveyed. Other synonyms include ascertained, checked, double-checked, ensured, and corroborated. These terms indicate that a certain action has been taken to ensure the accuracy of the information or situation being presented. Using synonyms for "made certain" can add variety to your writing and provide a clearer understanding of the situation.