The term 'text' can refer to a variety of written materials. A TOPIC is a general SUBJECT of discussion, while CONTENT is the specific information related to that TOPIC. A SUBJECT is a particular area of study, and a LIBRETTO is the text of an opera or musical. A WORKBOOK is a book of exercises related to a particular SUBJECT, and a SCHOOLBOOK is a book used in a school setting. A TEXTBOOK is a book used for instruction in a particular SUBJECT, and an EXCERPT is a passage taken from a longer work. A THEME is a central idea or message, and a VERSE is a line or group of lines in a poem. A MANUAL is a book of instructions, and WORDS are the smallest units of language. SMS stands for short message service, and BODY is the main part of a text. COPY is a duplicate of an original text, and PROSE is written language that is not poetry. An EDITOR is a person who prepares a text for publication, and a message is a communication sent from one person to another.