It appears that your statement might be incomplete, but based on what you've shared, it seems like you're referring to the classification of words or elements in languages, which is a common topic in linguistics. In many languages, words can generally be divided into two broad categories:

1. **Content Words (Open Class)**: These are words that carry significant meaning and can stand alone as complete ideas. They include nouns, verbs, adjectives, and some adverbs. Content words can easily enter and leave the lexicon of a language as new terms develop and old ones fall out of use.

2. **Function Words (Closed Class)**: These are words that primarily serve grammatical functions. They include articles, prepositions, conjunctions, and some adverbs. Function words typically do not change much over time and are fewer in number compared to content words.

If you intended to convey something different or if you have more context, please feel free to provide additional details!