Use the same term consistently for a specific thought or object
You will confuse your audience if you use different terms for the same concept. For example, if you use the term "senior citizens" to refer to a group, continue to use this term throughout your document. Don't substitute another term, such as "the elderly" or "the aged." Using a different term may cause the reader to wonder if you are referring to the same group.
Don't feel that you need to use synonyms to make your writing more interesting. Federal writers are not supposed to be creating great literature. You are communicating requirements, how to get benefits, how to stay safe and healthy, and other information to help people in their lives. While using different words may make writing more interesting, it may decrease clarity.