In biomedical research, the person who directs a research project or program. The principal investigator (the PI) usually writes and submits the grant application, oversees the scientific and technical aspects of the grant, and has responsibility for the management of the research.

The person(s) in charge of a clinical trial or a scientific research grant. The principal investigator prepares and carries out the clinical trial protocol (plan for the study) or research paid for by [..]

The person who is responsible for the scientific and technical direction of the entire clinical study (for example, for all sites of a multisite study).

in the context of European Research Council (ERC) grant schemes, means the individual researcher that submits Starting, Consolidator and Advanced Grant proposals on behalf of the host institution and who has scientific responsibility for the project.

An individual who conducts an investigation, ie, under whose immediate direction research is conducted, or, in the event of an investigation conducted by a team of individuals, is the responsible leader of that team.

The person or organization responsible for a study; equivalent to "author" in bibliographic citations.

A scientist who leads an Individual Project (IP) is a Principal Investigator (PI). He/she applies via the EUROCORES CRP for funding from a national funding organisation which is participating in a EUR [..]

The person or organization responsible for a study; equivalent to "author" in bibliographic citations.

PI Name of the person responsible for the technical and financial administration of a project and/or award.

According to 10 CFR 602.3 [Title 10 Energy; Chapter II Department of Energy; Subchapter H Assistance Regulations; Part 602 Epidemiology and other Health Studies Financial Assistance Program], the term [..]

The lead scientist for a particular well-defined science (or other academic) project. In the context of federal funding from agencies such as NASA or the NSF, the PI is the person who takes direct responsibility for completion of a funded project, directing the research, and reporting directly to the funding agency.

The individual officially responsible for the conduct of a sponsored project.  On research projects, the PI is usually a faculty member; on other types of awards, such as financial aid, the PI may have an administrative appointment.  The determination of PI eligibility is made at the tub level.

An individual designated by the institution to direct the project or activity being supported by external funding. He or she is responsible and accountable to the institution and sponsor for the prope [..]

the scientist in charge of a research team conducting clinical trials.

the big cheese/head honcho/primary cognizant entity associated with a project

 The individual primarily responsible for the taking, importation, export, and any related activities conducted under a permit issued for scientific research or enhancement.

The Laboratory manager or employee who has ultimate responsibility for meeting the terms of a project proposal, including the scope of work, the schedule, and the budget

A principal investigator is the lead scientist or engineer for a particular well-defined science project.