UPVC is a hard plastic used to make things that must sit outside for years without rotting — most often window frames and door frames, but also pipes, gutters, and cladding on the outside of houses. It is written in capitals because it is an abbreviation, and you say each letter: U-P-V-C. You will also see it written uPVC with a small u, which is actually the more technical spelling. Ordinary PVC, the plastic in raincoats and soft hoses, has softening chemicals added to make it bend; UPVC has none of them, so it stays stiff and strong. That is exactly what a window frame needs. The word belongs to builders, house adverts, and home-improvement shops, and it is used far more in Britain than in the United States, where people are more likely to say 'vinyl windows'. It is an uncountable noun and normally sits in front of another noun: UPVC windows, a UPVC door, UPVC pipes. In Taiwan you will hear this material talked about mostly in the context of imported or European-style windows; the everyday word is simply 塑鋼 or 塑鋼窗.

硬質聚氯乙烯（做門窗框的塑膠材料）；台灣一般直接說「塑鋼」或「塑鋼窗」