Open class words, commonly referred as content words, are those belonging to the major part of speech like noun, verbs, adjective and adverbs. These words include brother, run, tall, quickly etc.
In contrast, closed class words are those belonging to grammatical, or function, classes like articles, demonstrative, quantifiers, conjunctions and prepositions. It tends to include a small number of fixed elements. Function words in English include conjunction like (and, or), articles (a, the), demonstrators (this, that), quantifiers (most, few) or prepositions (to, after) etc.
The difference between open class words and close class words lies in use of telegraphic language. Generally, in telegraphic language, open class words are retained but close class words omitted.
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