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Certain types of rules or customs may become law and regulatory legislation may be introduced to formalize or enforce the convention (for example, laws that define on which side of the road vehicles must be driven). In a social context, a convention may retain the character of an "unwritten law" of custom (for example, the manner in which people greet each other, such as by shaking each other's hands).
In physical sciences, numerical values (such as constants, quantities, or scales of measurement) are called conventional if they do not represent a measured property of nature, but originate in a convention, for example an average of many measurements, agreed between the scientists working with these values.
A convention is a selection from among two or more alternatives, where the rule or alternative is agreed upon among participants. Often the word refers to unwritten customs shared throughout a community. For instance, it is conventional in many societies that strangers being introduced shake hands. Some conventions are explicitly legislated; for example, it is conventional in the United States and in Germany that motorists drive on the right side of the road, whereas in New Zealand and the United Kingdom motorists drive on the left. The standardization of time is a human convention based on the solar cycle or calendar. The extent to which justice is conventional (as opposed to natural or objective) is historically an important debate among philosophers.
The nature of conventions has raised long-lasting philosophical discussion. Quine, Davidson, and David Lewis published influential writings on the subject. Lewis's account of convention received an extended critique in Margaret Gilbert's On Social Facts (1989), where an alternative account is offered. Another view of convention comes from Ruth Millikan's Language: A Biological Model (2005), once more against Lewis.[example needed]
According to David Kalupahana, The Buddha described conventions—whether linguistic, social, political, moral, ethical, or even religious—as arising dependent on specific conditions. According to his paradigm, when conventions are considered absolute realities, they contribute to dogmatism, which in turn leads to conflict. This does not mean that conventions should be absolutely ignored as unreal and therefore useless. Instead, according to Buddhist thought, a wise person adopts a middle way without holding conventions to be ultimate or ignoring them when they are fruitful.
In sociology a social rule refers to any social convention commonly adhered to in a society. These rules are not written in law or otherwise formalized. In social constructionism there is a great focus on social rules. It is argued that these rules are socially constructed, that these rules act upon every member of a society, but at the same time, are re-produced by the individuals.
Sociologists representing symbolic interactionism argue that social rules are created through the interaction between the members of a society. The focus on active interaction highlights the fluid, shifting character of social rules. These are specific to the social context, a context that varies through time and place. That means a social rule changes over time within the same society. What was acceptable in the past may no longer be the case. Similarly, rules differ across space: what is acceptable in one society may not be so in another.
Social rules reflect what is acceptable or normal behaviour in any situation. Michel Foucault's concept of discourse is closely related to social rules as it offers a possible explanation how these rules are shaped and change. It is the social rules that tell people what is normal behaviour for any specific category. Thus, social rules tell a woman how to behave in a womanly manner, and a man, how to be manly. Other such rules are as follows:
- Strangers being introduced shake hands, as in Western societies, but
- Bow toward each other, in Korea, Japan and China
- Wai each other in Thailand
- Do not bow at each other, in the Jewish tradition
- In the United States, eye contact, a nod of the head toward each other, and a smile, with no bowing; the palm of the hand faces sideways, neither upward nor downward, in a business handshake.
- Present business cards to each other, in business meetings (both-handed in Japan)
- Click heels together, while saluting in some military contexts 
- A woman's curtsey, in some societies
- In the Middle East, never displaying the sole of the foot toward another, as this would be seen as a grave insult.
- In many schools, though seats for students are not assigned they are still "claimed" by certain students, and sitting in someone else's seat is considered an insult
In government, convention is a set of unwritten rules that participants in the government must follow. These rules can be ignored only if justification is clear, or can be provided. Otherwise, consequences follow. Consequences may include ignoring some other convention that has until now been followed. According to the traditional doctrine (Dicey), conventions cannot be enforced in courts, because they are non-legal sets of rules. Convention is particularly important in the Westminster System of government, where many of the rules are unwritten.
The term "convention" is also used in international law to refer to certain formal statements of principle such as the Convention on the Rights of the Child. Conventions are adopted by international bodies such as the International Labour Organization and the United Nations. Conventions so adopted usually apply only to countries that ratify them, and do not automatically apply to member states of such bodies. These conventions are generally seen as having the force of international treaties for the ratifying countries. The best known of these are perhaps the several Geneva Conventions.
- Edwards, Phil (7 October 2016). "Why people never smiled in old photographs". Vox.
- David Kalupahana, Nagarjuna: The Philosophy of the Middle Way. SUNY Press, 1986, pages 17-18. The author refers specifically to the thought of the Buddha here.
- "Rendering Honours". moebius.freehostia.com. Retrieved 2019-04-21.