P (named pee ) is the 16th letter of the modern English alphabet and the ISO basic Latin alphabet.

An emoticon ( or ), etymologically a portmanteau of emotion and icon, is a metacommunicative pictorial representation of a facial expression that, in the absence of body language and prosody, serves to draw a receiver's attention to the tenor or temper of a sender's nominal non-verbal communication, changing and improving its interpretation. It expresses — usually by means of punctuation marks (though it can include numbers and letters) — a person's feelings or mood, though as emoticons have become more popular, some devices have provided stylized pictures that do not use punctuation.

Overpressure ammunition, commonly designated as +P or +P+, is small arms ammunition that has been loaded to a higher internal pressure than is standard for ammunition of its caliber (see internal ballistics), but less than the pressures generated by a proof round. This is done typically to produce rounds with a higher muzzle velocity and stopping power, such as ammunition used for defensive purposes. Because of this, +P ammunition is typically found in handgun calibers which might be used for defensive purposes.

P* (pronounced "P-star") is a programming language meant to be useful in web development for creating dynamic HTML documents. The language provides syntax for templates and prepared SQL-statements. P* programs are scripts which are run by the P* interpreter.

P. is an abbreviation or acronym that may refer to:

• Page (paper), where the abbreviation comes from Latin pagina
• Paris Herbarium, at the Muséum national d'histoire naturelle
• Pani (Polish), translating as Mrs.
• The Pacific Reporter
• Pádraig Flynn, a former Irish politician

PI may refer to:

• Isoelectric point, the pH at which a particular molecule or surface carries no net electrical charge.
• Parental investment, in evolutionary biology
• Paternity Index, a value used to calculate probability of paternity
• Phosphatidylinositol, a class of lipids
• Pistillata, a gene that influences the development of flowers in the ABC model of flower development
• Plasticity index, a measure of the plasticity of a soil
• Polyimide, a polymer of imide monomers
• Ponderal index, a measure of leanness of a person (similar to body mass index)
• Principal investigator, the lead scientist or engineer for a particular project
• Propidium iodide, a chemical used as a DNA stain
• Protease inhibitor (pharmacology), class of drugs used to treat or prevent infection by viruses, including HIV and Hepatitis C
• Protease inhibitor (biology), molecules that inhibit the function of proteases
• Pulsatility index, a ratio of blood flow rates

The PROTON Ontology (PROTo ONtology) is a basic upper-level ontology that contains about 300 classes and 100 properties, providing coverage of the general concepts necessary for a wide range of tasks, including semantic annotation, indexing, and retrieval of documents.

Pascal is a historically influential imperative and procedural programming language, designed in 1968–69 and published in 1970 by Niklaus Wirth as a small and efficient language intended to encourage good programming practices using structured programming and data structuring.

The Pentium III (marketed as Intel Pentium III Processor, informally PIII, also stylized as Pentium !!! ) brand refers to Intel's 32-bit x86 desktop and mobile microprocessors based on the sixth-generation P6 microarchitecture introduced on February 26, 1999. The brand's initial processors were very similar to the earlier Pentium II-branded microprocessors. The most notable differences were the addition of the SSE instruction set (to accelerate floating point and parallel calculations), and the introduction of a controversial serial number embedded in the chip during the manufacturing process.

The peseta (, ) was the currency of Spain between 1869 and 2002. Along with the French franc, it was also a de facto currency used in Andorra (which had no national currency with legal tender).

The number is a mathematical constant, the ratio of a circle's circumference to its diameter, commonly approximated as 3.14159. It has been represented by the Greek letter "" since the mid-18th century, though it is also sometimes spelled out as "pi" .

A prime number (or a prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself. A natural number greater than 1 that is not a prime number is called a composite number. For example, 5 is prime because 1 and 5 are its only positive integer factors, whereas 6 is composite because it has the divisors 2 and 3 in addition to 1 and 6. The fundamental theorem of arithmetic establishes the central role of primes in number theory: any integer greater than 1 can be expressed as a product of primes that is unique up to ordering. The uniqueness in this theorem requires excluding 1 as a prime because one can include arbitrarily many instances of 1 in any factorization, e.g., 3, 1 · 3, 1 · 1 · 3, etc. are all valid factorizations of 3.

The proton is a subatomic particle, symbol or , with a positive electric charge of +1e elementary charge and mass slightly less than that of a neutron. Protons and neutrons, each with mass approximately one atomic mass unit, are collectively referred to as "nucleons". One or more protons are present in the nucleus of every atom. The number of protons in the nucleus is the defining property of an element, and is referred to as the atomic number. Since each element has a unique number of protons, each element has its own unique atomic number. The word proton is Greek for "first", and this name was given to the hydrogen nucleus by Ernest Rutherford in 1920. In previous years Rutherford had discovered that the hydrogen nucleus (known to be the lightest nucleus) could be extracted from the nuclei of nitrogen by collision. The proton was therefore a candidate to be a fundamental particle and a building block of nitrogen and all other heavier atomic nuclei.

(majuscule: , minuscule: ) is a Latin P with a diacritical tilde. It is or was used as a grapheme in some languages of Vanuatu, such as North Efate, South Efate and Namakura, to represent a . It is also used in the Yanesha language.

The sound recording copyright symbol, represented by the graphic symbol ℗ (a circled capital letter P), is the copyright symbol used to provide notice of copyright in a sound recording (phonogram) embodied in a phonorecord (LPs, audiotapes, cassettes, compact discs, etc.). The use of the symbol originated in United States copyright law and is specified internationally in the Convention for the Protection of Producers of Phonograms Against Unauthorized Duplication of Their Phonograms.