Examples of open-class words are those belonging to the major part-of-speech classes (nouns, verbs, adjectives, and adverbs), which in any language tend to be quite large and 'open-ended.' that is, an unlimited number of new words can be created and added to these classes. . . .
"One familiar variety of language in which the distinction between open-class words and closed-class words is important is known as telegraphic speech. The term telegraphic derives from the kind of language used in telegrams, where considerations of space (and money) force one to be as terse as possible. HAVING WONDERFUL TIME; HOTEL GREAT; RETURNING FLIGHT 256; SEND MONEY; STOP. Generally speaking, in telegraphic forms of language the open-class words are retained, whereas the closed-class words are omitted wherever possible.