a procedure to allow a nonparty, called an intervenor (also spelled intervener) to join ongoing litigation, either as a matter of right or at the discretion of the court, without the permission of the original litigants. The basic rationale for intervention is that a judgment in a particular case may affect the rights of nonparties, who ideally should have the right to be heard.
is . . . 'both physical procedures by which data are gathered . . . and manipulations of the subject or the subject's environment that are performed for research purposes.