"Upper case letters" are a common term used to describe capital letters in writing. However, there are several synonyms for this term that can be used interchangeably. One such synonym is "capital letters," which is often preferred by typographers and graphic designers. Another synonym is "majuscule letters," which comes from the Latin word "majusculus," meaning "larger." Other synonyms for "upper case letters" include "big letters," "block letters," and "capitalized letters." No matter which term you use, it's important to remember that these letters are used for proper nouns, the first word in a sentence, or for emphasis.