Closed-class word

Closed-class words belong to a list of morphemes that can be considered complete and it is normally rare to find new words added to this list by the very nature of their functions as function words.
The types of words which are listed as closed-class are:

• auxiliary verb - always inflected
• conjunction - uninflected
• determiner - uninflected
• preposition - uninflected
• pronoun - uninflected