Wiktionary
n. 1 The general welfare of the people; the best interests of the community. 2 (context economics English) A good that is non-rivalrous and non-excludable.
Wikipedia
In economics, a public good is a good that is both non-excludable and non-rivalrous in that individuals cannot be effectively excluded from use and where use by one individual does not reduce availability to others. Gravelle and Rees: "The defining characteristic of a public good is that consumption of it by one individual does not actually or potentially reduce the amount available to be consumed by another individual." In a non-economic sense, the term is often used to describe something that is useful for the public generally, such as education and infrastructure, although these are not "public goods" in the economic sense. This is in contrast to a common good which is non-excludable but is rivalrous to a certain degree.
Public goods include fresh air, knowledge, national security, common language(s), flood control systems, lighthouses, and street lighting. Public goods that are available everywhere are sometimes referred to as global public goods. There is an important conceptual difference between the sense of 'a' public good, or public 'goods' in economics, and the more generalized idea of 'the public good' (or common good, or public interest),"‘the’ public good is a shorthand signal for shared benefit at a societal level [this] (philosophical/political) sense should not be reduced to the established specific (economic) sense of ‘a’ public good."
Many public goods may at times be subject to excessive use resulting in negative externalities affecting all users; for example air pollution and traffic congestion. Public goods problems are often closely related to the "free-rider" problem, in which people not paying for the good may continue to access it. Thus, the good may be under-produced, overused or degraded. Public goods may also become subject to restrictions on access and may then be considered to be club goods or private goods; exclusion mechanisms include copyright, patents, congestion pricing, and pay television.
There is a good deal of debate and literature on how to measure the significance of public goods problems in an economy, and to identify the best remedies.
Usage examples of "public good".
The citizens of Mars shall, over the course of their lives, give one m-year of work to global service and the public good, such work to be defined by the economic commission, but never to be military or police work.
Pray bring to your mind how often I desired you to consider, when you insisted on the motive of public good.
This I have since often known to have been taken with success, and do freely recommend it to my countrymen, for the public good, as an admirable specific against all diseases produced by repletion.
Some say: self-sacrifice for humanity, the public good, the cult of the beautiful, and so forth.
Had he been able to enter any other profession, his genius might have been stunted to a mere pastime, instead of being, as now, utilised for the public good.