I changed slide title from Words as Common Goods to Words as Public Goods.

Use of words by one person does not diminish their availability to others. In economic terms, public goods are non-excludable and non-rivalrous.

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I wrote "words are common goods", but I wonder I should write "words are public goods". How do you think?

The choice between "words are common goods" and "words are public goods" depends on the specific meaning you want to convey.

Common Goods: This term often refers to resources that are shared by a group but are not necessarily owned by the public or the state. Common goods are accessible to all members of the group, but they are not unlimited and can be depleted or overused. In the context of words, using "common goods" might suggest that words are a shared resource among a community or group, implying a sense of shared ownership and responsibility.

Public Goods: Public goods are typically resources that are freely accessible to all members of the public, cannot be easily restricted, and their use by one person does not diminish their availability to others. In economic terms, public goods are non-excludable and non-rivalrous. If you say "words are public goods," it implies that words are freely available to everyone and their use by one person does not prevent their use by another, aligning with the characteristics of public goods in economics.

The context in which you are using this phrase would guide which term is more appropriate. If you are emphasizing the shared nature and potential for depletion or overuse, "common goods" might be more suitable. If you are emphasizing the unrestricted and non-depletable nature of words, "public goods" would be a better choice.