Consent
In a legal or sexual context, two persons are said to consent when they agree upon the same thing in the same sense. In common speech, "'consent'" can also mean "'to give permission'", or "'to yield'"; it is important to note the context in order to identify which meaning is meant.
Types
Implied consent is a controversial form of consent which is not expressly granted by a person, but rather inferred from a person's actions and the facts and circumstances of a particular situation (or in some cases, by a person's silence or inaction). Some examples include implied consent to follow rules and/or regulations at an education institution.
Express consent is clearly and unmistakably stated, rather than implied. It may be given in writing, by speech (orally), or non-verbally, e.g. by a clear gesture such as a nod. Non-written express consent not evidenced by witnesses or an audio or video recording may be disputed if a party denies that it was given.
Informed consent in medicine is consent given by a person who has a clear appreciation and understanding of the facts, implications, and future consequences of an action. The term is also used in other contexts.