> The economic definition of a public good is something that cannot be effectively owned. While I am aware the definition of a public good, your definition is

> The economic definition of a public good is something that cannot be effectively owned. While I am aware the definition of a public good, your definition is not appropriate because flood control systems, lighthouses, and street lighting can be owned. The problem the root comment touches is excessive use and for all of the above examples that are scarce (fresh air, common language, flood control systems, lighthouses, street lighting) there can be excessive use to the detriment of others and it can be avoided if these items are private property. For others (the non-scarce - knowledge, language) you cannot take away the rights for others to use it. So there is no real sense in claiming it a public good because there is really nothing. Finally, official statistics and national security depend too much on the definition to say to which category the belong.