The phrase "my word" is a commonly used expression to emphasize the truthfulness or sincerity of a statement. However, if one wants to mix up their vocabulary, there are many other synonyms that can be used instead. These include "I promise," "I swear," "I guarantee," "I assert," and "I attest." Each of these phrases carries a slightly different connotation, with "I promise" implying a personal commitment, "I swear" adding an element of solemnity, and "I guarantee" suggesting a level of confidence in the statement. By using different synonyms for "my word," writers and speakers can add variety and nuance to their language and better express their intentions.