Trust is a relationship between two entities or elements. It consists a set of activity and security policy in which element x trusts element y if and only if x has confidence that y will behave in a well-defined way that does not violate the given security policy.
One party (trustor) is willing to rely on the actions of another party (trustee); the situation is directed to the future. In addition, the trustor (voluntarily or forcedly) abandons control over the actions performed by the trustee. As a consequence, the trustor is uncertain about the outcome of the other's actions; they can only develop and evaluate expectations. The uncertainty involves the risk of failure or harm to the trustor if the trustee will not behave as desired.