"Make certain" is a common phrase that refers to ensuring that something is true or guaranteed. There are many synonyms for this phrase, including "verify," "confirm," "assure," "establish," "guarantee," "certify," "validate," "ascertain," and "ensure." These words all suggest a sense of confidence and certainty, and they can be used interchangeably. For example, one might say "I will make certain that the report is accurate" or "I will verify that the report is accurate." By using different synonyms for "make certain," you can add variety and precision to your writing or speech, while still conveying the same basic meaning.