Fringe vocabulary refers to vocabulary that is more specific to a topic, environment, or individual. Fringe vocabulary is not generic and is not likely to be used across environments, but is used in a specific setting with certain communication partners. In our conversations, fringe words constitute only 20% of what we speak, as compared to Core words, which constitutes 80% of the words we speak. 

Fringe words are typically nouns and are used much less frequently in conversations and do not contribute to language development like the way core words do. Hence building up Fringe vocabulary, which seems an easier task, doesn't help with developing the users's language and expression. 

E.g. In the sentence "I want to play with my teddy" - 

"teddy" is a fringe word, which can be used only in this specific context of toys. The  rest of the words in the sentence are Core words that can be used in any context. 

E.g. I love eating ice-cream

Ice-cream is a fringe word, as it is a noun and is used in a specific context only. Whereas the remaining words can be used across multiple contexts. 

It is important to not give too much importance to building up fringe vocabulary, thought it appears seemingly easier to teach the child, as they are typically objects that are more tangible for the child. It is easy to be misled into believing that the child has learnt a lot of "vocabulary" with fringe words, but will be unable to express themselves beyond making requests. Other expressions such as expression of feelings, comments, asking questions will remain under-developed. 

E.g. Consider the following example: 

User A's vocabulary - 10 words - box, ball, teddy, toilet, bottle, water, 

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