What is corruption? (See below a discussion of characteristics of corruption).
The simplest definition is:
Corruption is the misuse of public power (by elected politician or appointed civil servant) for private gain.
In order to ensure that not ony public corruption but also private corruption between individuals and businesses could be covered by the same simple definition:
Corruption is the misuse of entrusted power (by heritage, education, marriage, election, appointment or whatever else) for private gain.
This broader definition covers not only the politician and the public servant, but also the CEO and CFO of a company, the notary public, the teamleader at a workplace, the administrator or admissions-officer to a private school or hospital, the coach of a soccerteam, etcetera.
A much more difficult, scientific definition for the concept ‘corruption’ was developed by profesor (emeritus) dr. Petrus van Duyne:
Corruption is an improbity or decay in the decision-making process in which a decision-maker consents to deviate or demands deviation from the criterion which should rule his or her decision-making, in exchange for a reward or for the promise or expectation of a reward, while these motives influencing his or her decision-making cannot be part of the justification of the decision.