Open and Closed Word Class

Open Word Class

Open word class is a category of words (known as parts of speech) that finds new words. For example, before the invention of computer technology, words like browse, download, internet, fax, etc. did not exist. Open word class includes: 

Nouns

Lexical Verbs

Adjectives

Adverbs

Closed Word Class

Closed word class is a category of words that don't accept any new members. That is no new words of these categories are created. Closed word class includes: 

Prepositions

Pronouns

Conjunctions

Modal Verbs

Be Verbs

Auxiliary verbs