PI
Abbreviation with 12 meanings
| Stands for | Personal injury |
|---|---|
| Meanings | 12 |
| Categories | Law & Legal, Medical, Education & Academia, Sports, Units & Measurements, Business & Finance |
PI has 12 meanings. The most common are Personal injury (litigation) and Pressure injury (nursing); it can also stand for Principal investigator, Preliminary injunction, Pass interference, Package insert and Protease inhibitor, plus 5 more listed below.
Meanings of PI at a glance
| # | PI stands for | Context |
|---|---|---|
| 1 | Personal injury | Law & Legal › Litigation |
| 2 | Pressure injury | Medical › Nursing |
| 3 | Principal investigator | Education & Academia › Academic |
| 4 | Preliminary injunction | Law & Legal › Litigation |
| 5 | Pass interference | Sports › American Football |
| 6 | Package insert | Medical › Pharmacy |
| 7 | Protease inhibitor | Medical › Drug Class |
| 8 | Prediction interval | Units & Measurements › Statistics |
| 9 | Professional indemnity insurance | Business & Finance › Insurance |
| 10 | Profitability index | Business & Finance › Finance |
| 11 | Proteasome inhibitor | Medical › Drug Class |
| 12 | Program increment | Business & Finance › Project Management |
1. Personal injury
Law & Legal · Litigation Abbreviations
Area of law covering claims for physical or psychological harm caused by someone else's negligence or intentional conduct, such as car crashes, falls, medical malpractice and defective products. PI lawyers usually represent injured plaintiffs on a contingency fee.
Example: She hired a PI firm that takes a third of any recovery and nothing if the case is lost.
Contingency fees in personal injury commonly range from 33 to 40 percent, and some states cap them in medical malpractice cases. Most PI claims settle with insurers without a trial. Related no-fault auto coverage is called personal injury protection (PIP). Outside law, PI usually means private investigator or, in research, principal investigator.
2. Pressure injury
Medical · Nursing Abbreviations
Localized damage to skin and underlying tissue, usually over a bony prominence or under a medical device, caused by sustained pressure or pressure with shear. It is staged 1 to 4, unstageable, or deep tissue pressure injury.
Example: Stage 2 PI to sacrum 2 x 1.5 cm, base pink, no tunneling, foam dressing applied.
The term replaced "pressure ulcer" in 2016, when the National Pressure Ulcer Advisory Panel (renamed the National Pressure Injury Advisory Panel in 2019) revised its staging. Older terms include bedsore and decubitus ulcer. Stages are never "reverse staged" as a wound heals; a healing stage 3 stays a stage 3.
3. Principal investigator
Education & Academia · Academic Abbreviations · also used in medicine
Scientist or scholar who leads a research project and holds primary responsibility for its design, conduct, budget, compliance and reporting to the funding agency. In academic labs "the PI" is simply the lab head who supervises students, postdocs and staff.
Example: Ask the PI before ordering anything over $500 on the grant.
The National Institutes of Health has allowed multiple PIs on a single grant since 2007, while the National Science Foundation lists one PI plus co-PIs. A PI's name appears first on grant applications and is accountable for research integrity. Outside research, PI can mean private investigator or the number pi.
4. Preliminary injunction
Law & Legal · Litigation Abbreviations
Court order issued after notice and a hearing that requires or forbids specific conduct while a lawsuit is pending, to prevent irreparable harm before final judgment. The movant must usually show likely success on the merits, irreparable harm, a favorable balance of equities and that the injunction serves the public interest.
Example: After a two-day evidentiary hearing, the court granted the PI and set the bond at $250,000.
The four-factor test was restated in Winter v. NRDC (2008), and Rule 65(c) requires the movant to post security. Orders granting or denying a PI can be appealed immediately. In Trump v. CASA (2025) the Supreme Court held that federal courts likely lack authority to issue universal injunctions protecting nonparties. In injury law, PI instead means personal injury.
5. Pass interference
Sports · American Football Abbreviations
Foul in which a player illegally hinders an opponent's chance to catch a forward pass while the ball is in the air. It can be called on the defense or the offense and is one of the most consequential penalties in football.
Example: A late PI flag in the end zone gave the Saints first and goal at the 1.
Largely a judgment call, it was made reviewable by replay for the 2019 season after a missed call in the Rams-Saints NFC Championship Game, an experiment dropped after one year. Defensive and offensive interference are written DPI and OPI.
6. Package insert
Medical · Pharmacy Abbreviations
FDA-approved professional labeling that accompanies a prescription drug, also called prescribing information. It covers indications, dosing, contraindications, warnings, adverse reactions, interactions and pharmacology, and is the legal reference for how a drug may be marketed.
Example: Per the PI, reduce the dose by half when CrCl is below 30 mL/min.
Since the FDA's 2006 Physician Labeling Rule, US prescribing information opens with a one-page "Highlights" section, and serious risks appear in a boxed warning at the top. Prescribing outside the PI's indications ("off-label") is legal, but manufacturers may not promote it. In nursing PI often means pressure injury.
7. Protease inhibitor
Medical · Drug Class Abbreviations
Antiviral drugs that block viral protease enzymes needed to produce mature virus particles. HIV protease inhibitors include darunavir, atazanavir and lopinavir, usually boosted with ritonavir or cobicistat; hepatitis C and COVID-19 drugs such as glecaprevir and nirmatrelvir are also PIs.
Example: Resistance on INSTI regimen: switch to boosted PI darunavir/cobicistat.
Saquinavir, approved in 1995, was the first HIV protease inhibitor, and combining PIs with NRTIs ushered in highly active antiretroviral therapy in 1996. Boosted PIs have a high barrier to resistance but cause many CYP3A4 interactions. In oncology PI may mean proteasome inhibitor, and in labeling, package insert.
8. Prediction interval
Units & Measurements · Statistics Abbreviations
A range expected to contain a single future observation with a stated probability, as opposed to a confidence interval for a mean or parameter. Prediction intervals are always wider because they include the variability of individual values.
Example: The model forecasts next month's sales at 1,200 units (95% PI 950 to 1,450).
A regression line's confidence band narrows as the sample grows, but its prediction band can never shrink below the scatter of individual points. Forecasting software such as R's forecast package shades 80 and 95 percent prediction intervals as a fan. In research administration, PI usually means principal investigator.
9. Professional indemnity insurance
Business & Finance · Insurance Abbreviations
Commonwealth term for insurance covering professionals against claims that negligent advice or services caused a client loss, the equivalent of errors and omissions insurance in the US.
Example: Architects in the scheme must hold PI cover of at least £2 million.
Many professional bodies, such as those for accountants, solicitors and surveyors, require members to carry PI. In finance, PI means profitability index.
10. Profitability index
Business & Finance · Finance Abbreviations
Capital-budgeting ratio equal to the present value of a project's future cash flows divided by its initial investment. A PI above 1.0 corresponds to a positive NPV, and the ratio helps rank projects when capital is limited.
Example: With $1.3 million of discounted inflows on a $1 million outlay, the project's PI is 1.3.
Also called the benefit-cost ratio or value investment ratio. PI is useful under capital rationing because it shows value created per dollar invested, but it can favor small projects over larger ones that create more total value. Outside finance, PI commonly means principal investigator or private investigator.
11. Proteasome inhibitor
Medical · Drug Class Abbreviations
Cancer drugs that block the proteasome, the cell's protein-recycling complex, causing toxic protein buildup in malignant plasma cells. Bortezomib, carfilzomib and oral ixazomib are cornerstones of multiple myeloma treatment.
Example: VRd: bortezomib (PI) 1.3 mg/m2 subcut, lenalidomide, dexamethasone; acyclovir prophylaxis.
Bortezomib, approved in 2003, was the first proteasome inhibitor. Giving it subcutaneously rather than IV reduces nerve damage, its main toxicity. Shingles reactivation is common, so antiviral prophylaxis is standard. Carfilzomib carries a higher risk of heart and kidney problems. In HIV care PI means protease inhibitor, a completely different class.
12. Program increment
Business & Finance · Project Management Abbreviations
Fixed timebox in the Scaled Agile Framework, typically 8 to 12 weeks, during which an agile release train plans and delivers value, beginning with a PI planning event.
Example: The PI Planning session brought 90 people together for two days.
SAFe 6.0, released in 2023, renamed it "planning interval" while keeping the PI abbreviation. In finance, PI means profitability index.
Related abbreviations
More litigation abbreviations
- Opp'n – Opposition
- OSC – Order to show cause
- PACER – Public Access to Court Electronic Records
- Pet'r – Petitioner
- PJ – Personal jurisdiction
- Pl. – Plaintiff
- PO – Protective order
- POS – Proof of service
See all 71 litigation abbreviations →
More nursing abbreviations
- OGT – Orogastric tube
- OOB – Out of bed
- PERRL – Pupils equal, round, reactive to light
- PERRLA – Pupils equal, round, reactive to light and accommodation
- PICC – Peripherally inserted central catheter
- PIV – Peripheral intravenous catheter
- QSEN – Quality and Safety Education for Nurses
- ROC – Resumption of care
See all 90 nursing abbreviations →
This entry is for general education and is not medical or legal advice. Abbreviation use varies between institutions; always confirm in context.