Fraternization (from Latin frater, brother) is "turning people into brothers"—conducting social relations with people who are actually unrelated and/or of a different class (especially those with whom one works) as though they were siblings, family members, personal friends or lovers.
In many institutional contexts (such as militaries, diplomatic corps, parliaments, prisons, law enforcement or police, schools, sports teams, gangs, and corporations) this kind of relation transgresses legal, moral or professional norms forbidding certain categories of social contact across socially or legally defined classes. The term often therefore tends to connote impropriety, unprofessionalism or unethical behavior.
For example, "fraternization with the enemy" refers to associations with members of enemy groups and suggests a serious conflict of strong, deep, and close romantic interest and attraction, if not the possibility of treason; while "fraternization with civilians" typically suggests transgression of norms forbidding non-civilians and civilians to form close nonprofessional relationships (e.g., romantically), and "fraternization of officers with enlisted personnel" or "seniors with their juniors" (the usual referent of 'fraternization' in a military context) describes associations which are implied to be irregular, unprofessional, improper or imprudent in ways that negatively affect the members and goals of the organization.
A vast number of institutions worldwide implement policies forbidding forms of fraternization for many specific reasons. Fraternization may be forbidden to maintain image and morale, to protect and ensure fair and uniform treatment of subordinates, to maintain organizational integrity and the ability to achieve operational goals, and to prevent unauthorized transfers of information. Relations and activities forbidden under these anti-fraternization policies range from romantic and sexual liaisons, through gambling and ongoing business relationships, through insubordination, to excessive familiarity and disrespect of rank.
Views on fraternization are mixed and may depend on the relations and classes under discussion. Organizations may relax, change, or reinforce restrictions to reflect changes in the prevailing organizational view or doctrine regarding fraternization.
Within militaries, officers and members of enlisted ranks are typically prohibited from personally associating outside of their professional duties and orders. Excessively familiar relationships between officers of different ranks may also be considered fraternization, especially when between officers in the same chain of command. The reasons for anti-fraternization policies within modern militaries often include the maintenance of discipline and chain of command and the prevention of the spreading of military secrets to enemies, which may amount to treason or sedition under military law. (For an example of the former, consider a fighting force in which officers are unwilling to put certain enlisted men at risk; for an example of the latter, consider a situation in which a senior officer passes secrets to a junior officer, who allows them to be compromised by a romantic interest and consequently to end up in the hands of the enemy).
In order to impress the German people with the Allied opinion of them, a strict non-fraternization policy was adhered to by General Dwight D. Eisenhower and the War Department during World War II. However, thanks to pressure from the U.S. State Department and individual U.S. congressmen, this policy was eventually lifted in stages. In June 1945 the prohibition against speaking with German children was made less strict. In July it became possible to speak to German adults in certain circumstances. In September the no contact policy was abandoned in Austria and Germany. In the earliest stages of the occupation U.S. soldiers were not allowed to pay maintenance for a child they admitted having fathered, since to do so was considered as "aiding the enemy". Marriages between white U.S. soldiers and Austrian women were not permitted until January 1946, and with German women until December 1946.
In educational settings
Many schools and universities prohibit certain relationships between teachers/lecturers and students to avoid favoritism, coercion, sexual harassment and/or sex crimes enabled by the teacher's position of authority. These prohibitions are controversial, however, as they may come into conflict with rules on tenure (e.g., because unethical conduct is suspected but has not led to a conviction).
In the workplace
Court decisions in some U.S. states have allowed employers a limited legal right to enforce non-fraternization policies among employees (i.e., policies forbidding employees to maintain certain kinds of relationships with each other). Since the 1990s, such corporate policies have been increasingly adopted in the United States in the pursuit of objectives such as protecting professionalism and workplace productivity, promoting gender equality and women's rights, or avoiding and mitigating the impact of sexual harassment lawsuits. These decisions and the policies they protect have, however, been criticized on various grounds: as illegitimate constraints on individual freedom of association, as tools for companies to punish participation in labor unions, and as expressions of overzealous political correctness.
Professional and college-level sports teams in the U.S. have enacted anti-fraternization policies between athletes and cheerleaders. Very few American Football teams  allow casual contacts between players and cheerleaders. Reasons for this policy include interference with concentration, potential fallout for the images of teams, and the possibility of sex crimes or sexual harassment, and attendant legal liability.
- Varns, Nicola (December 2005). "It Started With a Kiss. Happy and tragic German-American love stories after World War II.". The Atlantic Times.
- Dangerous Liaisons: The Anti-Fraternization Movement In The U.S. Occupation Zones Of Germany And Austria, 1945-1948 by Perry Biddiscombe, Journal of Social History 34.3 (2001) 611-647
- washingtoncitypaper.com - Fraternization Row