Polyethylene terephthalate (sometimes written poly (ethylene terephthalate), commonly abbreviated PET, PETE, or the obsolete PETP or PET-P, is the most common thermoplastic polymer resin of the polyester family and is used in fibers for clothing, containers for liquids and foods, thermoforming for manufacturing, and in combination with glass fiber for engineering resins. Plastics like PET most likely touch your everyday life. Polyethylene Terephthalate, known commonly as PET or PETE is best known as the clear plastic used for water and soda bottle containers. As a raw material, PET is globally recognized as a safe, non-toxic, strong, lightweight, flexible material that is 100% recyclable. In fact, it’s THE most widely recycled plastic in the world! Virtually all municipal recycling programs in the US accept PET packaging, with recycling of thermoformed PET containers on the rise (let’s keep that trend going!). PET can be identified by looking at the bottom or backs of containers for the #1 resin identification code – a symbol recognized by the #1 in the middle surrounded by “chasing arrows”.

Because PET is an excellent water and moisture barrier material, plastic bottles made from PET are widely used for soft drinks. For certain specialty bottles, such as those designated for beer containment, PET sandwiches an additional polyvinyl alcohol (PVOH) layer to further reduce its oxygen permeability.

Biaxially oriented PET film (often known by one of its trade names, "Mylar") can be aluminized by evaporating a thin film of metal onto it to reduce its permeability and to make it reflective and opaque (MPET). These properties are useful in many applications, including flexible food packaging andthermal insulation. See: "space blankets". Because of its high mechanical strength, PET film is often used in tape applications, such as the carrier formagnetic tape or backing for pressure-sensitive adhesive tapes.

Non-oriented PET sheet can be thermoformed to make packaging trays andblister packs. If crystallizable PET is used, the trays can be used for frozen dinners, since they withstand both freezing and oven baking temperatures. As opposed to amorphous PET, which is transparent, crystallizable PET or CPET tends to be black in colour.
When filled with glass particles or fibres, it becomes significantly stiffer and more durable. PET is also used as a substrate in thin film solar cells.

Terylene (a trademark formed by inversion of (polyeth)ylene ter(ephthalate)) is also spliced into bell rope tops to help prevent wear on the ropes as they pass through the ceiling. PET is used since late 2014 as liner material in type IV composite high pressure gas cylinders. PET works as a much better barrier to oxygen than earlier used (LD)PE