The term 'Dictionary Subject' can be broken down into two crossword solutions: USAGE (5 letters) and StandardEnglish (15 letters). USAGE refers to the way words are used in a language, including their pronunciation, spelling, and grammar. StandardEnglish is the form of English that is accepted as the most correct and widely used form of the language. It is often used in formal writing and speech, and is the basis for most dictionaries.