open word class
Definition - A word class that CAN have new words added to it.

For example, the noun word class is open because new nouns can and are being added to it as the need arises (e.g. Internet, Facebook, and email).

As opposed to closed word classes — such as preposition, pronoun, determiner, and conjunction — which are accepting no new members.

1. Words in a open word class are called open-class items.

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