1) Informed consent is a decision to participate in research, taken by a competent individual who has received the necessary information; who has adequately understood the information; and who, after considering the information, has arrived at a decision without having been subjected to coercion, undue influence or inducement, or intimidation
CIOMS, International Ethical Guidelines for Biomedical Research Involving Human Subjects, Geneva 2002, Commentary on Guideline 4, General considerations
2) A process by which a subject voluntarily confirms his or her willingness to participate in a particular trial, after having been informed of all aspects of the trial that are relevant to the subject's decision to participate. Informed consent is documented by means of a written, signed and dated informed consent form.
International Conference on Harmonisation (ICH) – Guideline for Good Clinical Practice (GCP) E6 (R1), art. 1.28