Poly

Poly can have multiple meanings:

As a prefix, often meaning more than one or many (e.g., polyvalent - capable of many valences)
As a feminine given name (Poly, also spelled Polly). Sometimes also used as a nickname for surnames such as "Polyblank"

Poly is also commonly used as an abbreviation for various words and phrases including:

Science and technology

Polyethylene, polyurethane and polyester, all forms of plastic polymers
Polysilicon, a state of silicon used as a gate material in MOSFET transistors and CMOS microchips
Polystyrene, aromatic polymer made from the aromatic monomer styrene
Poly-A, a step in the transcription of DNA to RNA in which multiple adenosine nucleosides are added to the 3' end of the mRNA sequence.
Polymorphism, polymorphism describes multiple possible states for a single property
Polyphenol, a class of biological molecules
Polyspheric, a shape composed of more than one sphere, a term used by Chrysler to identify their hemi-derived but lower cost V8 engines built 1955-67
Polygraph, or "lie detector" (particularly in Defense & Intelligence fields)

Mathematics and logic

Polygon, especially in relation to 3D graphics as used in terms such as high-poly
Polynomial, a type of mathematical function

Universities

Other

Polyamory, polygamy, and certain other forms of nonmonogamy beginning in poly
Polyclinic, a clinic where a wide range of health care services (including diagnostics) can be obtained without the need for an overnight stay
Polytechnic educational institutions
Polymath, a person well educated in a wide variety of subjects or fields
Polydactyly, having extra digits in hands or feet
Polymita, Business Process Management Suite
Poly Technologies, Chinese company
China Poly Group, Chinese business group
Polynesian, as in "Being a Poly" by Jonah Takalua
Polyglot, a person who uses many languages
Polyphasic sleep, the practice of sleeping multiple times in a 24-hour period
Polytheism is the belief in and/or worship of multiple deities