Trust is a relationship of reliance. A trusted party is presumed to seek to fulfill policies, ethical codes, law and their previous promises.
Trust does not need to involve belief in the good character, vices, or morals of the other party. Persons engaged in a criminal activity usually trust each other to some extent.
Trust is a prediction of reliance on an action, based on what a party knows about the other party.
In the social sciences, the subtleties of trust are a subject of ongoing research. In sociology (and psychology) the degree to which one party trusts another is a measure of belief in the honesty, benevolence and competence of the other party. Based on the most recent research, a failure in trust may be forgiven more easily if it is interpreted as a failure of competence rather than a lack of benevolence or honesty.
From this perspective, trust is a mental state, which cannot be measured directly.
A critical element in studies of trust behavior is power. One who is in a position of dependence cannot be said to trust another in a moral sense. . . Trusting another party when one is compelled to do so is sometimes called reliance, to indicate that the belief in benevolence and competence may be absent, while the behaviors are present.
In general, trust is essential as Social institutions (governments), economies, and communities require trust to function. Therefore trust and altruism are areas of study for economists, although these concepts go beyond strict rational economics.